znbtc characterization map

Contents

(1) The baseband of Samsung i9300 is i9300znlg1 and the internal version number is IMM76D. What version is I9300ZNALG1 and what is the difference between different internal version numbers

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Chapter 1 Atomic Structure and Periodic System of Elements

Summarization of test points: Looking at the questions about atomic structure and periodic system of elements in chemical test questions in recent years, there are roughly the following test points:
1. Determine the position of new elements in the periodic table of elements, and predict its nature.
2. Investigate innovation ability. Break the normal arrangement of elements in the three-dimensional world, and let the contestants perform the electronic arrangement of elements or redraw the periodic table of elements under new conditions or “rules”, and speculate on the valence and properties of elements.
3. According to the relationship between several elements, infer their position in the periodic table.
4. Apply knowledge of chemistry, physics and other disciplines to inspect the latest scientific and technological achievements.
Trend prediction: In the future chemistry competition questions, more emphasis will be placed on the connection between chemistry and physics knowledge points, and the application of the knowledge of atomic structure and periodic system of elements in daily life. To examine the creative thinking ability of contestants to break “old knowledge” and build “new knowledge”. The author believes that if the above-mentioned knowledge points are examined, they will still make a fuss about the above-mentioned aspects.
I. Relative atomic mass
The relative atomic mass (atomic weight) of an element refers to the ratio of 1 molar mass of an element to 1/12 of the 12C molar mass of the nuclide. This definition shows that: ① The relative atomic mass of an element is a pure number. ② The relative atomic mass of a mononuclide element is equal to the relative atomic mass of the nuclide of the element. ③ The relative atomic mass of a multinuclide element is equal to the weighted average of the relative atomic masses of the natural isotopes of the element.
2. Atomic structure
(1) Bohr planetary model of atomic structure (extranuclear electron motion)
1. Hydrogen atom spectrum
In 1833 Balmer found the hydrogen atom spectrum The relationship between the wavelengths of each spectral line in the visible region is that B is a constant.
In 1913, Rydberg concluded that the general relationship between spectral lines is ν=R (1/n12-1/n22), R is the Rydberg constant, and its value is 3.19×1015 cycles/ Second. The relationship between the above formulas n1 and n2 corresponding to the spectral lines of each region is:
Ultraviolet region: n1=1, n2=2, 3, 4…
Visible region: n1=2, n2=3, 4 , 5….
Infrared region: n1=3, n2=4, 5, 6…
2. Bohr’s theory (characteristics of movement of electrons outside the nucleus)
1913 On the basis of Planck’s quantum theory, Einstein’s photonic theory and Rutherford’s model of nucleated atoms, Bohr put forward three hypotheses of atomic structure theory in order to clarify the results of hydrogen atom spectroscopy experiments, which are called The main points of Bohr’s theory are as follows:
①The electron outside the nucleus does not move around the nucleus in any orbit, but the orbital angular momentum P must meet the following conditions:
P=nh/2π, n is positive Integer, h is Planck’s constant. Orbits that meet the above conditions are called stable orbits, and electrons moving in stable orbits do not emit energy.
②The farther the electron’s orbit is from the nucleus, the higher the energy. Usually the electron moves in the orbit closest to the nucleus, when the energy of the atom is the lowest, called the ground state. When atoms gain energy from the outside world, electrons can jump to high-energy orbits farther away from the nucleus, which are called excited states.
③The excited state is unstable, electrons will transition from higher energy levels to lower energy levels, and release excess energy in the form of light.

At the same time, Bohr also calculated and derived the energy formula according to classical mechanics and quantization conditions:

Bohr’s theory has great limitations, it can only explain hydrogen atoms spectrum, cannot explain the atomic spectrum of the multi-electron system, or even the fine structure of the hydrogen spectrum. At the beginning of the 19th century, due to experiments such as light interference, diffraction and photoelectric effect, people had some understanding of the special law of microscopic particle motion—wave-particle duality. These two properties were quantitatively linked by Planck’s constant, E. =hν P=h/λ, thus revealing the essence of light well. where E is energy, P is momentum, λ is wavelength, and h is Planck’s constant. Later, electron diffraction experiments proved that the wavelength of electrons is λ=h/mυ, m is the mass of electrons, and υ is the speed of electron motion.
(2) Quantum Quantum of Hydrogen Atomic Structure (Extranuclear Electron Movement State)The mathematical model
①Probability density and electron cloud
|Ψ|2 represents the probability of electrons appearing in a unit volume element in the extra-nuclear space, which is called the probability density. The product of the probability density and the total volume of the region is the probability of electrons appearing in the region.
The electron cloud is an image describing the movement of electrons in the outer space. It is related to the probability density |Ψ|2. It visualizes the probability density of the outer electrons from the statistical concept. ‘s icon. That is, a specific image of |Ψ|2.
②Physical meaning of the four quantum numbers
a. The principal quantum number n It represents the number of layers of electrons, the average distance between electrons and the nucleus and the level of energy. Values ​​are 1, 2, 3, …, 0 (positive integer).
b. Angular quantum number l It determines the shape of the atomic orbital (or electron cloud), and takes the value of 0, 1, 2, …, (n-l). For example, when l=0, it is an s orbit with a star-shaped distribution; when l=1, it is a p orbital with a dumbbell-shaped distribution; when l=2, it is a d orbital with a petal-shaped distribution. In a multi-electron system, l is also related to energy, such as the energy of each sub-layer orbital in the same main layer is different, that is, Ens<Enp<End
c. The magnetic quantum number m, which determines the atomic orbital (or electron cloud) ) in the extension direction of space. The values ​​are 0, ±1, ±2, …, ±l. For example, when l=1, m can have three values, namely 0, +1, -1, indicating that the p sublayer orbital has three different stretches Direction, namely px, py, pz three tracks.
d. Spin quantum number ms It does not depend on n, l, m, and is not the result of solving the Schrödinger equation, but the result of experimental determination. It proves that the electron rotates clockwise or counterclockwise around its own axis. The value is +1/2 or -1/2, respectively.
3. The arrangement of electrons outside the nucleus, the periodic system of elements and the periodicity of elements
1. The arrangement of electrons outside the nucleus: ① The principle of the lowest energy. ② Pauli exclusion principle. ③Hunt’s rule.
2. Shielding effect In multi-electron atoms, due to the repulsion of other electrons to a certain electron, part of the nuclear charge is offset, resulting in a decrease in the effective nuclear charge and weakening the attraction of the nuclear charge to the electron. This effect is called shielding or shielding effect. As a result of the shielding effect, different sub-layer orbitals with the same principal quantum number undergo energy level splitting. l small electrons, the shielding effect of other electrons on it is small, and its energy is low, namely: Ens<Enp<Endnp>nd>nf. The deeper the electron drills, the less shielded it is from other electrons, the stronger the attraction to the nucleus, and thus the lower the energy. Therefore, the order of the orbital energy of each sublayer with the same n and l different is Ens<Enp<End<Enf. When both n and l are different, energy level interleaving occurs, that is, E4s<E3d. This phenomenon is related to the drill-through effect of electrons. Since the penetrating ability of 4s electrons is stronger than that of 3d, although the maximum peak of 4s is farther from the nucleus than that of 3d, but because it has a small peak drilled very close to the nucleus, it has a great influence on reducing the orbital energy, so that E4s<E3d.
4. The relationship between the atomic structure and the position of the element in the periodic table
①The period number of the element The value of n in the outermost layer of the atom is the period number of the element. An energy level group is equivalent to a cycle, and the cycle is divided into long and short. Short period (only s and p energy levels are contained in the energy level group). Long period (in addition to s and p energy levels, the energy level group also contains d and f energy levels).
②Element group number Elements with the same valence electron structure form a group. Clan is divided into main clan and sub clan. The main group is usually called the A group, and the subgroup is called the B group.
A group element: its group number is equal to the electrons on the ns and np layers, such as 3s23p4, which is the third period VIA group element.
B group elements: a. When the total number of electrons on the (n-1)dns layer is 3~7, the number of electrons is the B group number of the element. For example, 5d56s2 is the sixth period VIIB group element.
b. When the total number of electrons on the (n-1) dns layer is 8~10, they are all elements of group VIII, such as 3d84s2, which is the element of group VIII of the fourth period.
c. When (n-1)d10ns, the total number of electrons on the ns layer is the B group number. For example, 4d105s2 is the fifth periodic group II element.
③ Grouping of elements in the periodic table

5. The periodic relationship between atomic structure and element properties
①Atomic radius The changing law of atomic radius in the periodic table: in the same main group from top to bottom, with the increase of the number of electron layers, the atomic radius increases in turn. Although the nuclear charge increases from top to bottom, which tends to shrink the atomic radius, it is not the main factor. Group B elements do not change significantly, especially the elements of the fifth and sixth periods, due to the shrinkage of the lanthanide series, making their radii very similar. In the same period, for short periods, as the number of nuclear charges increases from left to right, the attracting ability of the nucleus to the outer electrons increases correspondingly, and the atomic radius gradually decreases. For long periods, as the nuclear charge increases, the newly added electrons fill the (n-1)d orbital. For determining the atomic radiusFor the outermost electron layer of ��, the shielding effect of the electrons on the sub-outer layer is much greater than the shielding effect of the outermost electrons from each other, so most of the nuclear charge increasing from left to right is Shielded by the increased (n-1)d electrons, that is, the effective nuclear charge increases relatively slowly, so the atomic radius decreases slightly from left to right. When the electronic layer structure is (n-1)d10, the atomic radius is slightly increased due to the large shielding effect of the outer electrons. When the electronic layer structure is (n-2)f7 and (n-2)f14, the atomic radius also increases slightly, and the atomic radius of the rare gas at the end of each cycle suddenly increases. (The radius of the noble gas is the van der Waals radius).
②Electronegativity The ionization potential and electron affinity of an element only reflect the ability of an atom to gain or lose electrons from one aspect, and both have certain limitations in fact. When atoms combine with each other, the difficulty of losing electrons and the difficulty of gaining electrons must be considered together. The ability or ability of an atom to attract electrons in a molecule is usually called the electronegativity of an element. According to the size of the electronegativity of the element, the strength of the metallicity and non-metallicity of the element is uniformly measured. The electronegativity of elements also shows periodic changes, and the general trend of change is that the same cycle increases from left to right, and the same family decreases from top to bottom. Therefore, in the periodic table, the element fluorine in the upper right is the most electronegative, that is, the most non-metallic, and the cesium in the lower left is the least electronegative, that is, the most metallic.
4. Use s, p, d, etc. to represent the ground state configuration (including neutral atoms, positive ions and negative ions)

Chapter II Molecular Structure

Competition point induction: The judgment of molecular structure is the most basic knowledge of chemistry, and it is also the knowledge point examined in chemistry competitions. In recent years, the knowledge points that often appear when examining molecular structures in chemistry competitions are as follows:
1. According to the hybrid orbital theory, determine the hybrid state of the central atom.
2. Determine the shape of the molecule according to Lewis electron theory.
3. According to the valence shell electron pair repulsion theory, determine the shape of the molecule.
4. Determine the structure of the unknown molecule according to the isoelectronic principle.
Of course, there are various forms of examination questions, and the form of examination is not a single one, but often a combination of various forms. Based on years of training experience, the author believes that when participants learn about molecular structure, they should first learn Lewis electron theory, and then learn valence electron pair repulsion theory. Lewis electron theory can be learned on the basis of the first two theories.
Trend prediction: In the future, the examination of molecular structure in chemistry competition questions will still be an important part of the examination of participants’ spatial perception ability, and the intensity of the examination may be increased. Hard to come up with an answer. The investigation of molecular structure may increase the amount of information and examine the latest scientific and technological achievements in recent years. In short, since the judgment of molecular structure will involve mathematical knowledge, from the perspective of testing the overall quality of the contestants, the questions about molecular structure will always be the main questions of the chemistry competition.
I. Lewis structural formula
American chemist Lewis believes that the two atoms that constitute a substance each take out an electron to form a pair, and the substance is formed by the mutual combination of this shared electron pair. He also believes that the outermost electron configuration of the noble gas is a stable configuration, and other atoms tend to share electrons so that their outermost layer is converted into the 8-electron stable configuration of the noble gas – the octagonal law. Lewis also called the chemical force held together by a “shared electron pair” as a covalent bond. Later generations called this concept the Lewis theory of covalent bonds. In addition to the bonding electrons used to form covalent bonds, there are often non-bonded electrons that are not used to form covalent bonds, also known as lone pair electrons. Later generations called this structural formula with a lone pair of electrons added as the Lewis structural formula.
2. Single bond, double bond and triple bond – σ bond and π bond
The characteristic of the σ bond is that the two atomic orbitals overlap in the direction of the bond axis in a “head-to-head” manner, and the overlapping part is along the direction of the bond axis. The key shaft is cylindrically symmetrical. This method has a large degree of overlap, so the bond energy of the σ bond is large and the stability is high. A pi bond is characterized by the overlapping of two atomic orbitals in a parallel, or “side-by-side” manner, with the overlap being mirror-antisymmetric to a plane passing through one bond axis. It has less overlap, so it is less stable.
3. Valence Shell Electron Repulsion Model (VSEPR)
The configuration of the molecule mainly depends on the mutual repulsion of electron pairs (including bonding electron pairs and lone electron pairs) in the valence electron shell. . The configuration of the molecule is always the one with the least repulsion between the electron pairs.
①If the central atomic valence shell electron pairs are all bonding electron pairs, it is very simple to judge the configuration.
Example of electron logarithmic configuration
2 Linear BeCl2, HgCl2
3 Planar triangle BF3, BCl3
4 Regular tetrahedron CH4, NH4+, CCl4, SiCl4
5 Triangular bipyramid PCl5, PF3Cl2, SbCl5
6 Positive��hedral SF6, MoF6
②If the central atomic valence shell electron pair contains a lone electron pair, then each lone electron pair occupies a position corresponding to a single bond electron pair (for the same single bond position, it can be arbitrarily selected. , for unequal single bonds, the principle of minimum repulsion between electron pairs should be selected. For example, in the triangular bipyramid, lone electron pairs are only allowed to occupy any single bond position in the plane triangle).
③If there is a double bond or triple bond in the molecule, the electron pair repulsion theory still applies, and the double bond is regarded as a single bond. For example, the CO2 molecule is linear O=C=O.
④The repulsive force between the valence electron pair depends on the angle between the electron pair and the bonding condition of the electron pair. The smaller the angle between the electron pairs, the greater the repulsive force. The order of repulsion between electron pairs is lone electron pair-repulsion between lone electron pair>lone electron pair-repulsion between bonding electron pair>bonding electron pair-repulsion between bonding electron pair.
⑤ The count of the number of electron pairs in the valence electron shell of the central atom, that is, the sum of the number of valence electrons of the central atom plus the number of electrons supplied by the ligand is divided by 2. When the oxygen group atoms are used as ligands, it can be considered that they do not provide shared electrons (such as the central atom P of PO43+, 5 valence electrons, plus 3 charges, a total of 8 electrons, that is, 4 pairs of valence electrons), but when the oxygen group When an atom acts as a central atom, it can be considered that it provides 6 valence electrons (for example, the center of SO3 provides 6 valence electrons to S, and oxygen as a ligand does not provide electrons, so the valence electron pair of the central atom S is 3 pairs). If the substance in question is a cation, such as NH4+, the central atom has a total of 5 N valence electrons 2s22p3, plus one electron from each of the four ligands, minus one charge, a total of 8 electrons, that is, 4 pairs of valence electrons.
4. Hybrid orbital theory
The main point is that during the formation of molecules, due to the mutual influence of atoms, different types of atomic orbitals with similar energies are mixed to form a new set of hybrid hybrids with the same energy Orbitals, the number of hybrid orbitals is equal to the number of atomic orbitals that make up the hybrid orbitals; the hybrid orbitals are divided into two types: equal and unequal hybrids; when the hybrid orbitals form a bond, the maximum overlap of the orbitals is required, and the bond and the The repulsion between the keys is minimal.
Sterical configuration example of isotropic hybrid orbital type angle molecules
sp hybrid 1080 linear BtCl3
sp2 hybrid 1200 planar triangular HgCl2
sp3 hybrid 109028/ positive Tetrahedral CH4, SiH4, NH4+
sp3d2 Hybrid 900 and 1800 Regular octahedral SF6
Inequality hybrid orbital type (there are lone pairs of electrons in the hybrid orbital)
Inequality sp3 Hybrid 104045/ Triangular H2O H2S
10705/ Triangular Pyramid NH3 PH3
V. Conjugated Large π Bond and Isoelectronic Principle
(1) pp Large π Bond in Benzene Molecule
In the Lewis structure of benzene, the carbon-carbon bond is divided into single bond and double bond. This structure satisfies the four valence of carbon. However, in fact, I have learned in middle school chemistry that all carbon-carbon bonds of benzene molecules are There is no difference between bond length and bond energy. This contradiction can be solved by the concept that the carbon atoms of the benzene ring form pp large π bonds – the carbon atoms in the benzene molecule take sp2 hybridization, and the three hybrid orbitals are used to form three σ bond, so the benzene molecule has a σ skeleton of a plane structure with a bond angle of 1200; each carbon atom of the benzene molecule still has a p orbital that is not involved in hybridization, which is perpendicular to the molecular plane and parallel to each other. Obviously, there is no difference between the adjacent carbon atoms on the left and right of each carbon atom. It is considered that the electron in the p orbital of a carbon atom that is not involved in hybridization and hybridization only forms a σ bond with one electron in the parallel p orbital of the left adjacent carbon atom. Instead of forming a π bond with the parallel p orbital of the right adjacent carbon atom or the opposite is obviously illogical, it is better to think that all 6 “side by side” parallel p orbitals have a total of 6 electrons together to form a dispersion throughout the benzene ring. pp large pi bond.
(2) pp large π bond in butadiene
The molecular formula of butadiene is H2C=CH-CH=CH2. All 4 carbon atoms are adjacent to 3 atoms, so sp2 heterozygous , these hybrid orbitals overlap each other to form the molecular sigma skeleton, so that all atoms are in the same plane. Each carbon atom also has an uninvolved hybrid p orbital, perpendicular to the molecular plane, with one electron in each p orbital. Therefore, there is a p-p large π bond with “4 orbitals and 4 electrons” in the butadiene molecule. Usually ∏ a b is the symbol of the large π bond, where a represents the number of parallel p orbitals, and b represents the number of electrons in the parallel p orbitals. In addition, CO2 molecules, CO32- and O3 molecules all contain large π bonds.
(3) The principle of isoelectronics
Has the same general formula – AXm, and the molecules or ions with the same total number of valence electrons have the same structural characteristics, this principle is called “the principle of isoelectronics”. Such as: CO2, CNS-, NO2+, N3- have the same general formula – AX2, the total number of valence electrons is 16, and have the same structure – linear molecules, there are no lone pairs of electrons on the central atom and take sp hybrid orbitals to form Linear σ skeleton, the bond angle is 1800, there are two sets of ∏ 4 3 pp large π bonds in the molecule. Similarly SO2, O3, NO2- are isoelectronic bodies, SO42- and PO43- are isoelectronic bodies.
6. Properties of covalent molecules and intermolecular forces
(1) Bond parameters are some physical quantities that characterize the properties of valence bonds, such as bond order, bond energy, bond angle, bond length, bond polarity sex data.
① Bond order = (number of bonding electrons – number of anti-bonding electrons)/2
② Bond energy: For AB-type diatomic molecules, the bond energy is the dissociation energy D.
For polyatomic molecules, bond energy is the average dissociation energy of multiple bonds, such as: N-H bond energy of NH3 molecule
③ Bond length: the equilibrium distance between two nuclei in the molecule.
④ Bond angle: the angle between the bond and the bond in the molecule.
⑤ Bond polarity: Covalent bonds are divided into non-polar covalent bonds and polar covalent bonds, which can be measured by the difference in electronegativity between the two atoms involved in the bond formation. When the electronegativity difference is greater than 1.7, it can be regarded as an ionic bond; when the electronegativity difference is between 1.7 and 0, it can be regarded as a polar covalent bond; when the electronegativity difference is equal to zero, it is a non-polar covalent bond.
(2) Intermolecular forces and hydrogen bonds
1. Molecules can be divided into polar molecules and non-polar molecules. Polar molecules: the centers of gravity of positive and negative charges in the molecule do not overlap; non-polar molecules: the centers of gravity of positive and negative charges in the molecule overlap.
The polarity of a molecule is measured by the dipole moment µ, where µ=o. For non-polar molecules, the larger the µ, the stronger the polarity of the molecule.
µ=q.L
q is the charge on one end of the dipole, and L is the dipole distance of the molecule.
2. The intermolecular force is the van der Waals force, which is one or two orders of magnitude smaller than the chemical bond energy. It includes: ① Orientation force: the interaction force between permanent dipoles. ②Inductive force: the force between the induced dipole and the permanent dipole. ③ Dispersion force: the interaction force due to the instantaneous dipole.
3. Hydrogen bond Hydrogen bond can usually be expressed as X-H…Y, where X, Y represent F, O, N and other atoms with large electronegativity and small atomic radius. X and Y can be the same element or different elements.
Hydrogen bonds have directionality and saturation, and the bond energy is similar to the intermolecular force, which can be divided into two categories:
①Intermolecular hydrogen bonds: such as hydrogen bonds between H2O molecules
② Intramolecular hydrogen bonds: such as the hydrogen bonds in o-nitrophenol:
Chapter 3 Crystal Structure
Chapter Summary: Crystal structure is an important part of chemistry competition questions, because crystal structure can be tested for competition The spatial perception ability of the contestants can test the mathematical skills of the contestants. Therefore, after careful analysis of the chemistry competition questions in recent years, the crystal structure questions have the following forms:
1. Simply examine the three-dimensional structure of a crystal (mainly examine the cubic unit cell). Building the bridge between the micro and macro is Avogadro’s constant.
2. Examining atomic cluster compounds. Competitors are asked to understand what “chemical environment” means. Convex polyhedra often use Euler’s formula.
3. To examine the knowledge of crystal defects. The particles that make up the crystal have non-integer ratios. Learn about ions filling tetrahedral, octahedral, or cubic cavities.
4. Simple crystal structure, but need to establish a mathematical model to answer quickly. For example, by mathematical induction of chemical problems based on mathematical knowledge, a general formula can be obtained, and then chemical problems can be solved according to the general formula.
Trend prediction: In recent years, chemistry competition questions have shown a diversified trend when examining crystal structures. From examining simple crystal structures to examining structural questions that require mathematical models ” and other test questions. Therefore, the author believes that the knowledge depth of crystal structure test questions in the future will show a downward trend, but the ability requirements of the contestants will be higher and higher. That is to examine some questions in special circumstances, breaking old knowledge, building new knowledge and so on.
I. Crystals and Unit Cells (1) The essential feature of a crystal is its “self-normativeness”, that is, the crystal can spontaneously assume the shape of a closed regular convex polyhedron. It is divided into single crystal and double crystal, and some hungry crystalline substances cannot see the regular shape and are polycrystalline. The shapes of single crystals formed under natural conditions are rich and diverse. However, with the help of geometric knowledge, the same crystal planes can be found, and the dihedral angle between the determined crystal planes – “crystal plane angle” is unchanged. . It is called the law of constant angle between crystal planes.
In the microscopic space of the crystal, atoms are regularly arranged regularly. For an ideal perfect crystal, this periodicity is monotonic and invariant, which is a common feature of crystals and is called translational symmetry.
(2) The basic characteristics of the unit cell and the coordinates of the atoms in the unit cell and the counting unit cell have the same apex angle, the same parallel face and the same parallel edge. It is not a unit cell without translation. The geometric features of the parallelepiped can be determined by the relationship of side length and included angle. The side length and included angle of the Bravais unit cell are called unit cell parameters. It is usually expressed by a three-array consisting of x, y, and z in the vector xa+yb+zc.The positions of atoms in a cell are called atomic coordinates. The value range of the absolute value of atomic coordinates is 1>∣x(y,z) ∣≥0. A value of 1 is equivalent to a translation to another unit cell, no different from a value of zero.
(3) Elemental unit cell and complex unit cell – body-centered unit cell, face-centered unit cell, bottom-centered unit cell and 14 Bravais lattice types
The unit cell is the description of the crystal microstructure basic unit, but not necessarily the smallest unit. The prime unit cell is the smallest basic unit in the crystal microscopic space, and it cannot be any smaller. The set of atoms in the prime unit cell is equivalent to the smallest set of periodic translation of atoms in the microscopic space of the crystal, which is called a structural unit. The compound unit cell is the polyploid of the prime unit cell; there are three types of split heart unit cell (2-fold), face-centred unit cell (4-fold) and bottom-centre unit cell (2-fold).
(4) Bravais system 7 series and unit cells of prime and complex combination, there are only 14 kinds of unit cells in total, which is called Bravais lattice type in crystallography
2. Types of crystals
br />1. The particles on the lattice nodes in metal crystals are metal atoms or metal ions, and the binding force is metal bonds (free electrons). It is characterized by a large specific gravity, metallic luster, and electrical and thermal conductivity. , has good ductility and so on. The chemical forces between atoms in metal crystals are called metallic bonds. Metallic bonds are a type of delocalized chemical bonds that are spread throughout the crystal. Metal bond theory includes modified covalent bond theory and energy band theory.
2. Ionic crystals The crystals of the ionized species are ionic crystals, such as NaCl, CsCl, and the like. In an ionic crystal, the particles on the lattice nodes are positive and negative ions, and the force between the particles is electrostatic attraction. Crystals are characterized by high melting, boiling point and hardness, but are brittle, have poor ductility, and can conduct electricity in a molten state or in an aqueous solution. When an active metal atom with low electronegativity meets an active non-metallic atom with high electronegativity, positive and negative ions are formed due to electron transfer between atoms, and the chemical bond formed by electrostatic interaction is called ionic bond.
(1) The essence of ionic bond is electrostatic force, without directionality and saturation.
(2) The characteristics of the ion, that is, the charge of the ion, the radius of the ion and the configuration of the electron shell of the ion.
(3) There are the following types of electron shell configurations of ions:
2 Electron configuration: such as Li+, Be2+, ​​etc.
8 electron configuration: such as Na+, Ca2+ and some simple anions Cl-, O2+ and so on.
18 electron configuration: such as Zn 2+, Hg2+, Cu+, Ag+, etc.
18+2 electron configuration: that is, the sub-outer layer 18+ outermost layer 2, such as P2+, Sn2+ and so on.
9~17 Irregular configuration: such as Fe2+, Cr3+, Mn2+, etc.
(4) The strength of ionic bonds is usually measured by the size of the lattice energy U.

U can be calculated by using the Bonn-Haber cycle according to the relevant thermodynamic data,
3. Molecular crystals and atomic crystals such as CO2, HCl, I2, etc. In molecular crystals, the particles on the lattice nodes are molecules (including polar or non-polar), and the force between the particles is van der Waals attraction . There are covalent bonds between atoms in a molecule. Therefore, the melting and boiling points of the crystal are low, the hardness is small, the solid is non-conductive, and it is generally not conductive when it is melted. Only highly polar molecular crystals such as HCl dissolve in water and conduct electricity due to ionization. Such as diamond (C), Si, B, SiO2, SiC, BN, etc., the particles on the lattice nodes of the crystal are atoms, and the atoms are connected by covalent bonds. Therefore, its melting and boiling points are high, its hardness is high, and it is non-conductive and thermally conductive, but Si and SiC have semiconductor properties.
4. Mixed crystals, such as graphite, asbestos, mica, etc., have various forces in their crystals.
Taking graphite as an example, the particles in the layers (ie between C atoms) are bound by covalent bonds, and at the same time, there are free flowing electrons (equivalent to metal bonds), and the layers are connected by van der Waals attraction . Therefore, it has luster, can conduct electricity, conduct heat, and slide easily.
3. Atomic coordinates. The calculation of the number of atoms or molecules in the unit cell and the relationship with the chemical formula
Usually, the three arrays composed of x, y, and z in the vector xa+yb+zc are used to express the position of atoms in the unit cell, which is called atom coordinate. For example, the coordinates of the atoms located at the origin (vertex) of the unit cell are 0, 0, 0; the coordinates of the atoms located at the center of the unit cell are 1/2, 1/2, 1/2; the coordinates of the atoms located at the center of the ab face
The atomic coordinates of ac are 1/2, 1/2, 0; the atomic coordinates at the center of ac are 1/2, 0, 1/2; and so on. The value range of the absolute value of atomic coordinates is 1>|x(y,z)|≥0. A value of 1 is equivalent to shifting to another unit cell, which is no different from a value of 0. For example, the coordinates of the 8 atoms at the corners of the unit cell are all 0, 0, 0. Don’t forget: as long as one vertex of the unit cell has atoms, the other 7 vertexes must also have the same atoms, otherwise the parallelepiped loses translation and is not a unit cell. In the same way, the coordinates of the face-centered atoms of two parallel ab planes are 1/2, 1/2, 0, and one of them must have the other, otherwise it is no longer a unit cell. Conversely, the coordinatesEven if the same atoms are of the same kind, they cannot be regarded as equivalent. For example, atoms whose coordinates are 0, 1/2, and 1/2 are not equivalent.
4. The relationship between atomic packing and unit cell.

Chapter 4 Chemical Equilibrium
Induction of Match Points: In recent years, the solvated acid-base theory and chemical equilibrium knowledge have been examined many times in the exam questions of chemistry competitions. The main examination questions are:
1. Calculation of chemical equilibrium constants. Including calculation of thermochemical equilibrium constant, calculation of acid-base equilibrium constant, calculation of precipitation-dissolution equilibrium constant, calculation of coordination equilibrium constant, etc.
2. Non-aqueous solvent chemistry. Common non-aqueous solvents are BrF3, N2O4, liquid ammonia, liquid SO2, etc.
Trend prediction: Since the size of the chemical equilibrium constant can measure the feasibility of the reaction to a certain extent, the chemical equilibrium constant is the basis for quantitatively explaining the feasibility of the reaction, and must be a common content of the chemistry competition exam. The non-aqueous solvent is a substance that the contestants are not familiar with. In addition to reacting with many substances, it can also be related to the electrical conductivity of the substance and the ionization of the substance, so it can test the students’ ability to use the knowledge flexibly. The author believes that the above-mentioned competition questions will still appear in the future chemistry competition questions.
1. Chemical Equilibrium
When the reversible reaction proceeds to V positive = V inverse, or from the perspective of chemical thermodynamics, when the reversible reaction proceeds to its free energy change ⊿G=0, it is called chemical equilibrium condition. The chemical equilibrium state is a thermodynamic concept, which refers to a state in which the chemical reaction in the system has neither the spontaneity of the forward direction nor the spontaneity of the reverse direction. Thermodynamics assumes that all chemical reactions are reversible. When the chemical reaction reaches equilibrium, the concentrations or partial pressures of reactants and products no longer change, and the reaction “stagnates”, but this is only apparent, in essence, whatever The forward reaction or the reverse reaction is going on, so the chemical equilibrium is a kind of “dynamic equilibrium”. For example: Dissolution equilibrium, that is, a gas or solid dissolves in water (or other solvent), and finally a saturated solution is formed.
2. Equilibrium constant
1. When any reversible reaction reaches equilibrium at a certain temperature, the equilibrium constant of Aa+bB Dd+Ee
can be expressed as: K=[D]d[ E]e/[A]a[B]b Usually the equilibrium constant of the reversible reaction in solution is expressed by Kc, in this case the equilibrium concentration unit of each substance is mol/l, and the reversible reaction in gas phase is Kp
represents that the concentration of each substance at equilibrium is replaced by partial pressure. The relationship between Kc and Kp for the gas-phase reversible reaction is:

⊿n is the difference between the number of gas molecules before and after the reaction, which is equivalent to (d+e)-(a+b) in the reaction formula.
2. The physical meaning of the equilibrium constant
(1) The equilibrium constant is a characteristic constant of a reaction, which does not change with the initial concentration (or partial pressure) of the substance, but only depends on the nature of the reaction.
(2) The size of the equilibrium constant indicates the degree of the reversible reaction.
(3) The expression of the equilibrium constant indicates the condition for the system to reach equilibrium at a certain temperature.
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㈢ How to install Git in CentOS 7

Git server setup and client installation under CentOS
Time:2014-05-14 Source:blog.51cto.com
Outline:
1. Preface
2. Build a Git server
yum install a Git server
Create a git user to run the git service
Create a client Login certificate
Initialize Git repository
Disable shell login
Clone remote repository
Three, install client
Windows client
Linux client
Fourth, summary
Note, the test machine CentOS 5.5 x86_64, Git server version: git version 1.8.2.1, client version: git version 1.9.2.msysgit.0. Please download all software here: http://msysgit.github.io/.

I. Preface
In the last blog, we mainly explained what Git is, the basic principles of Git, and some basic knowledge about Git. Let us briefly understand Git, of course We still have a lot of problems to figure out, hehe! How about not managing, before we figure this out, we’re going to have to have a Git server right, hehe! Well, let’s build a Git server together.

Second, build Git server
1.yum install Git server

[[email protected] ~]# cd src/
[[email protected ] src]# wget http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
[[email protected] src]# rpm -ivh epel -release-5-4.noarch.rpm
Preparing… ################################ ########### [100%]
package epel-release-5-4.noarch is already installed
[[email protected] ~]# yum list
[[email protected] ~]# yum install -y git

2. Create a git user to run the git service

[[email protected] ~]# adser git

3. Create a client login certificate
Note, collect the public keys of all users who need to log in, which is the id_rsa.pub file they generated, and copy all the public keys to /home/git/.ssh/ In the authorized_keys file, one per line. Hey-hey!
1). The command for the client to generate the id_rsa.pub file

$ ssh-keygen -t rsa
$ cat .ssh/id_rsa.pub
ssh-rsa ++N3wEAQRYDmcYo1wmnm/4NQ+CAN45tqfsRuf58Uba9QNK7/6xSUiIKXQiILz8PMGJ3MnlV+== [email protected]

Note, just press Enter all the way, copy the generated id_rsa.pub to the administrator, and help you add it on the server , you won’t need to enter your username and password the next time you use git.
2). View the authorized_keys file on the server

[[email protected] ~]# cat /home/git/.ssh/authorized_keys
ssh-rsa wBVd++YmJFhqwkITNGccrO5sycROs9+ Fbjgd6oBSzNuaBtCIbwNNsEyM / henTl2euI3XsnJQ / ITr6c / q0P3WoGl4E2QFQ2kZqs ++ / + kJzJSKUTKDVSwY3 / + Q == [email protected]
ssh-rsa + PSK9PSg + bwiJ2iQRa39rXck35r + // RiCiYzd3RT / + S / LD3vx2MN + FNOHwvqcE + / 5yEqSgAkioa8SVMOsikYJG // RZ54Q == [email protected ]
ssh-rsa ++N3wEAQRYDmcYo1wmnm/4NQ+CAN45tqfsRuf58Uba9QNK7/6xSUiIKXQiILz8PMGJ3MnlV+== [email protected]

Note: I have three users logging into the server, so I have three ssh-rsa here , you can take a look.
4. Initialize the Git repository
Note, first select a directory as the Git repository, here is /data/git/project.git.

[[email protected] ~]# cd /data/git/
[[email protected] git]# git init –bare project.git
[[email protected ] project.git]# ls
branches config description HEAD hooks index info objects refs

Executing the Git command above will create a bare repository, and the bare repository has no workspace, because the Git repositories are purely for sharing, so users are not allowed to log in directly to the server to change the workspace, and Git repositories on the server usually end with .git. Then, change owner to git:

[[email protected] git]# chown -R git.git project.git
[[email protected] git]# ls -l
Total 4
drwxr-xr-x 7 git git 4096 05-09 13:50 project.git

5. Disable shell login
Note, for security reasons, The git user created in the second step does not allow a login shell, which can be done by editing the /etc/passwd file. Find a line similar to the following:

[[email protected] ~]# cat /etc/passwd | grep git
git:x:1001:1001:git version control:/home/git :/bin/bash

to:

[[email protected] ~]# vim /etc/passwd
git:x:1001:1001:git version control:/home/git:/usr/bin/git-shell

In this way, git users can use git through ssh normally, but cannot log in to the shell, because we specify git-shell for git users Automatically log out every time you log in.
6. Clone the remote repository
Note, now you can clone the remote repository through the git clone command, run on your own computer:

Note, $ git clone [email protected] :/data/git/project.git, where git username, git.jjhh.com server, /data/git/prgject.git is the repository path. Well, the construction of the server is completed here, let’s install the client.

Three, install the client
1. Windows client
1). Download the client
Note, you can download http://msysgit.github here. io/. The following is a brief demonstration of the installation process, which is relatively simple:

Okay, the installation is complete here. After installation, there will be an icon on the desktop, you can double-click to open it. As shown below:

2.Linux client
Note, the Linux client installation is relatively simple, just install it directly with yum!

1

[[email protected] ~]# yum install -y git

Here, the git installation is complete, let’s check it out Version:

1
2

[[email protected] ~]# git –version
git version 1.8.2.

Next we generate the public key and copy it to the server:

[[email protected] ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Created directory ‘/root/.ssh’.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
48:3c:22:76:02:f1:a2:e5:27:22:cb:4f:a7:a0:98:9d [email protected]
[[ email protected] ~]# cat .ssh/id_rsa.pub
ssh-rsa ++U7zP/hr6HzfqeZU09Ccis4yK3RMwip2f+/ug2M68Z0jQk5DVG8w5+/V7eOkrvBMDh9nDdwvDhPhuhBDSfE++B18MQ== [email protected]

Next, we copy the public key in id_rsa.pub to the authorized_keys file of the server.

[[email protected] ~]# su git
bash-3.2$ cd
bash-3.2$ vim .ssh/authorized_keys
ssh-rsa wBVd++ YmJFhqwkITNGccrO5sycROs9 + Fbjgd6oBSzNuaBtCIbwNNsEyM / henTl2euI3XsnJQ / ITr6c / q0P3WoGl4E2QFQ2kZqs ++ / + kJzJSKUTKDVSwY3 / + Q == [email protected]
ssh-rsa + PSK9PSg + bwiJ2iQRa39rXck35r + // RiCiYzd3RT / + S / LD3vx2MN + FNOHwvqcE + / 5yEqSgAkioa8SVMOsikYJG // RZ54Q == [ email protected]
ssh-rsa ++ N3wEAQRYDmcYo1wmnm / 4NQ + CAN45tqfsRuf58Uba9QNK7 / 6xSUiIKXQiILz8PMGJ3MnlV + == [email protected]
ssh-rsa ++ U7zP / hr6HzfqeZU09Ccis4yK3RMwip2f + / ug2M68Z0jQk5DVG8w5 + / V7eOkrvBMDh9nDdwvDhPhuhBDSfE ++ B18MQ == [email protected]

Next we clone a repository to a local directory.

[[email protected] ~]# cd /data/dev
[[email protected] dev]# git clone [email protected]:/data/git/project.git
Cloning into ‘project’…
The authenticity of host ‘git.jjhh.com (114.112.173.150)’ can’t be established.
RSA key fingerprint is ca:ec:a2: 7e:e6:89:ca:19:d3:93:7f:4b:c3:c0:c7:fd.
Are you sure you want to continue connecting (yes/no)? yes
Warning : Permanently added ‘git.jjhh.com,114.112.173.150’ (RSA) to the list of known hosts.
remote: Counting objects: 50, done.
remote: Compressing objects: 100% (42 /42), done.
remote: Total 50 (delta 21), reused 0 (delta 0)
Receiving objects: 100% (50/50), 4.02 KiB, done.
Resolving deltas: 100% (21/21), done.
[[email protected] dev]# ls
project
[[email protected] dev]# cd project/
[ [email protected] project]# ls
index.html

Well, here our git client is all installed here.

(iv) Mass fraction of 1, 3, 5—btc

Zn + 2HCl === ZnCl2 + H2↑
65 73 136 2
6.5gxyz
65/6.5g=73/x=136/y=2/z
x=7.3g
y=13.6g
z=0.2g1 mass of hydrogen 0.2g
2 The mass fraction of the solute in dilute hydrochloric acid is 7.3g/100g*100%=7.3%
3 The mass fraction of the solute in the solution after the reaction is 13.6g/(6.5g+100g-0.2g)*100%=12.8%

㈤ High school chemistry competition nouns, symbols summary and explanation />Summary of test points: Looking at the questions about atomic structure and periodic system of elements in chemical test questions in recent years, there are roughly the following test points:
1. Determine the position of a new element in the periodic table and predict its properties.
2. Investigate innovation ability. Break the normal arrangement of elements in the three-dimensional world, and let the contestants perform the electronic arrangement of elements or redraw the periodic table of elements under new conditions or “rules”, and speculate on the valence and properties of elements.
3. According to the relationship between several elements, infer their position in the periodic table.
4. Apply knowledge of chemistry, physics and other disciplines to inspect the latest scientific and technological achievements.
Trend prediction: In the future chemistry competition questions, more emphasis will be placed on the connection between chemistry and physics knowledge points, and the application of the knowledge of atomic structure and periodic system of elements in daily life. To examine the creative thinking ability of contestants to break “old knowledge” and build “new knowledge”. The author believes that if the above-mentioned knowledge points are examined, they will still make a fuss about the above-mentioned aspects.
I. Relative atomic mass
The relative atomic mass (atomic weight) of an element refers to the ratio of 1 molar mass of an element to 1/12 of the 12C molar mass of the nuclide. This definition shows that: ① The relative atomic mass of an element is a pure number. ② The relative atomic mass of a mononuclide element is equal to the relative atomic mass of the nuclide of the element. ③ The relative atomic mass of a multinuclide element is equal to the weighted average of the relative atomic masses of the natural isotopes of the element.
2. Atomic structure
(1) Bohr planetary model of atomic structure (extranuclear electron motion)
1. Hydrogen atom spectrum
In 1833 Balmer found the hydrogen atom spectrum The relationship between the wavelengths of each spectral line in the visible region is that B is a constant.
In 1913, Rydberg concluded that the general relationship between spectral lines is ν=R (1/n12-1/n22), R is the Rydberg constant, and its value is 3.19×1015 cycles/ Second. The relationship between the above formulas n1 and n2 corresponding to the spectral lines of each region is:
Ultraviolet region: n1=1, n2=2, 3, 4…
Visible region: n1=2, n2=3, 4 , 5….
Infrared region: n1=3, n2=4, 5, 6…
2. Bohr’s theory (characteristics of movement of electrons outside the nucleus)
1913 Bohr in Planck’s quantum theory, Einstein’s theory of photonics and Rutherford’s nucleated atom.On the basis of the �� type, in order to clarify the results of the hydrogen atomic spectrum experiment, three hypotheses of the atomic structure theory are proposed, which are called Bohr theory. The main points are as follows:
①The electrons outside the nucleus are not in any orbits To move around the nucleus, the orbital angular momentum P must meet the following conditions:
P=nh/2π, n is a positive integer, and h is Planck’s constant. Orbits that meet the above conditions are called stable orbits, and electrons moving in stable orbits do not emit energy.
②The farther the electron’s orbit is from the nucleus, the higher the energy. Usually the electron moves in the orbit closest to the nucleus, when the energy of the atom is the lowest, called the ground state. When atoms gain energy from the outside world, electrons can jump to high-energy orbits farther away from the nucleus, which are called excited states.
③The excited state is unstable, electrons will transition from higher energy levels to lower energy levels, and release excess energy in the form of light.

At the same time, Bohr also calculated and derived the energy formula according to classical mechanics and quantization conditions:

Bohr’s theory has great limitations, it can only explain hydrogen atoms spectrum, cannot explain the atomic spectrum of the multi-electron system, or even the fine structure of the hydrogen spectrum. At the beginning of the 19th century, due to experiments such as light interference, diffraction and photoelectric effect, people had some understanding of the special law of microscopic particle motion—wave-particle duality. These two properties were quantitatively linked by Planck’s constant, E. =hν P=h/λ, thus revealing the essence of light well. where E is energy, P is momentum, λ is wavelength, and h is Planck’s constant. Later, electron diffraction experiments proved that the wavelength of electrons is λ=h/mυ, m is the mass of electrons, and υ is the speed of electron motion.
(2) Quantum mechanical model of hydrogen atom structure (extranuclear electron motion state)
①Probability density and electron cloud
|Ψ|2 means that electrons appear in a unit volume element of extranuclear space is called the probability density. The product of the probability density and the total volume of the region is the probability of electrons appearing in the region.
The electron cloud is an image describing the movement of electrons in the outer space. It is related to the probability density |Ψ|2. It visualizes the probability density of the outer electrons from the statistical concept. ‘s icon. That is, a specific image of |Ψ|2.
②Physical meaning of the four quantum numbers
a. The principal quantum number n It represents the number of layers of electrons, the average distance between electrons and the nucleus and the level of energy. Values ​​are 1, 2, 3, …, 0 (positive integer).
b. Angular quantum number l It determines the shape of the atomic orbital (or electron cloud), and takes the value of 0, 1, 2, …, (n-l). For example, when l=0, it is an s orbit with a star-shaped distribution; when l=1, it is a p orbital with a dumbbell-shaped distribution; when l=2, it is a d orbital with a petal-shaped distribution. In a multi-electron system, l is also related to energy, such as the energy of each sub-layer orbital in the same main layer is different, that is, Ens<Enp<End
c. The magnetic quantum number m, which determines the atomic orbital (or electron cloud) ) in the extension direction of space. The values ​​are 0, ±1, ±2, …, ±l. For example, when l=1, m can have three values, namely 0, +1, -1, indicating that the p sublayer orbital has three different stretches Direction, namely px, py, pz three tracks.
d. Spin quantum number ms It does not depend on n, l, m, and is not the result of solving the Schrödinger equation, but the result of experimental determination. It proves that the electron rotates clockwise or counterclockwise around its own axis. The value is +1/2 or -1/2, respectively.
3. The arrangement of electrons outside the nucleus, the periodic system of elements and the periodicity of elements
1. The arrangement of electrons outside the nucleus: ① The principle of the lowest energy. ② Pauli exclusion principle. ③Hunt’s rule.
2. Shielding effect In multi-electron atoms, due to the repulsion of other electrons to a certain electron, part of the nuclear charge is offset, resulting in a decrease in the effective nuclear charge and weakening the attraction of the nuclear charge to the electron. This effect is called shielding or shielding effect. As a result of the shielding effect, different sub-layer orbitals with the same principal quantum number undergo energy level splitting. l small electrons, the shielding effect of other electrons on it is small, and its energy is low, namely: Ens<Enp<Endnp>nd>nf. The deeper the electron drills, the less shielded it is from other electrons, the stronger the attraction to the nucleus, and thus the lower the energy. Therefore, the order of the orbital energy of each sublayer with the same n and l different is Ens<Enp<End<Enf. When both n and l are different, energy level interleaving occurs, that is, E4s<E3d. This phenomenon is related to the drill-through effect of electrons. Since the penetrating ability of 4s electrons is stronger than that of 3d, although the maximum peak of 4s is farther from the nucleus than that of 3d, but because it has a small peak drilled very close to the nucleus, it has a great influence on reducing the orbital energy, so that E4s<E3d.
4. The relationship between the atomic structure and the position of the element in the periodic table
①The period number of the element The atom is the mostThe value of n in the outer layer is the period number of the element. An energy level group is equivalent to a cycle, and the cycle is divided into long and short. Short period (only s and p energy levels are contained in the energy level group). Long period (in addition to s and p energy levels, the energy level group also contains d and f energy levels).
②Element group number Elements with the same valence electron structure form a group. Clan is divided into main clan and sub clan. The main group is usually called the A group, and the subgroup is called the B group.
A group element: its group number is equal to the electrons on the ns and np layers, such as 3s23p4, which is the third period VIA group element.
B group elements: a. When the total number of electrons on the (n-1)dns layer is 3~7, the number of electrons is the B group number of the element. For example, 5d56s2 is the sixth period VIIB group element.
b. When the total number of electrons on the (n-1) dns layer is 8~10, they are all elements of group VIII, such as 3d84s2, which is the element of group VIII of the fourth period.
c. When (n-1)d10ns, the total number of electrons on the ns layer is the B group number. For example, 4d105s2 is the fifth periodic group II element.
③ Grouping of elements in the periodic table

5. The periodic relationship between atomic structure and element properties
①Atomic radius The changing law of atomic radius in the periodic table: in the same main group from top to bottom, with the increase of the number of electron layers, the atomic radius increases in turn. Although the nuclear charge increases from top to bottom, which tends to shrink the atomic radius, it is not the main factor. Group B elements do not change significantly, especially the elements of the fifth and sixth periods, due to the shrinkage of the lanthanide series, making their radii very similar. In the same period, for short periods, as the number of nuclear charges increases from left to right, the attracting ability of the nucleus to the outer electrons increases correspondingly, and the atomic radius gradually decreases. For long periods, as the nuclear charge increases, the newly added electrons fill the (n-1)d orbital. For the outermost electron layer, which determines the size of the atomic radius, the shielding effect of the electrons on the sub-outer layer is much greater than the shielding effect of the outermost electrons, so the nuclear charge increasing from left to right is absolutely Most of them are shielded by the increased (n-1)d electrons, i.e. the effective nuclear charge increases relatively slowly, so the atomic radius decreases slightly from left to right. When the electronic layer structure is (n-1)d10, the atomic radius is slightly increased due to the large shielding effect of the outer electrons. When the electronic layer structure is (n-2)f7 and (n-2)f14, the atomic radius also increases slightly, and the atomic radius of the rare gas at the end of each cycle suddenly increases. (The radius of the noble gas is the van der Waals radius).
②Electronegativity The ionization potential and electron affinity of an element only reflect the ability of an atom to gain or lose electrons from one aspect, and both have certain limitations in fact. When atoms combine with each other, the difficulty of losing electrons and the difficulty of gaining electrons must be considered together. The ability or ability of an atom to attract electrons in a molecule is usually called the electronegativity of an element. According to the size of the electronegativity of the element, the strength of the metallicity and non-metallicity of the element is uniformly measured. The electronegativity of elements also shows periodic changes, and the general trend of change is that the same cycle increases from left to right, and the same family decreases from top to bottom. Therefore, in the periodic table, the element fluorine in the upper right is the most electronegative, that is, the most non-metallic, and the cesium in the lower left is the least electronegative, that is, the most metallic.
4. Use s, p, d, etc. to represent the ground state configuration (including neutral atoms, positive ions and negative ions)

Chapter II Molecular Structure

Competition point induction: The judgment of molecular structure is the most basic knowledge of chemistry, and it is also the knowledge point examined in chemistry competitions. In recent years, the knowledge points that often appear when examining molecular structures in chemistry competitions are as follows:
1. According to the hybrid orbital theory, determine the hybrid state of the central atom.
2. Determine the shape of the molecule according to Lewis electron theory.
3. According to the valence shell electron pair repulsion theory, determine the shape of the molecule.
4. Determine the structure of the unknown molecule according to the isoelectronic principle.
Of course, there are various forms of examination questions, and the form of examination is not a single one, but often a combination of various forms. Based on years of training experience, the author believes that when participants learn about molecular structure, they should first learn Lewis electron theory, and then learn valence electron pair repulsion theory. Lewis electron theory can be learned on the basis of the first two theories.
Trend prediction: In the future, the examination of molecular structure in chemistry competition questions will still be an important part of the examination of participants’ spatial perception ability, and the intensity of the examination may be increased. Hard to come up with an answer. The investigation of molecular structure may increase the amount of information and examine the latest scientific and technological achievements in recent years. In short, since the judgment of molecular structure will involve mathematical knowledge, from the perspective of testing the overall quality of the contestants, the questions about molecular structure will always be the main questions of the chemistry competition.
I. Lewis structural formula
American chemist Lewis believes that the two atoms that make up matterEach takes out one electron to form a pair, and the substance is formed by the mutual combination of this shared electron pair. He also believes that the outermost electron configuration of the noble gas is a stable configuration, and other atoms tend to share electrons so that their outermost layer is converted into the 8-electron stable configuration of the noble gas – the octagonal law. Lewis also called the chemical force held together by a “shared electron pair” as a covalent bond. Later generations called this concept the Lewis theory of covalent bonds. In addition to the bonding electrons used to form covalent bonds, there are often non-bonded electrons that are not used to form covalent bonds, also known as lone pair electrons. Later generations called this structural formula with a lone pair of electrons added as the Lewis structural formula.
2. Single bond, double bond and triple bond – σ bond and π bond
The characteristic of the σ bond is that the two atomic orbitals overlap in the direction of the bond axis in a “head-to-head” manner, and the overlapping part is along the direction of the bond axis. The key shaft is cylindrically symmetrical. This method has a large degree of overlap, so the bond energy of the σ bond is large and the stability is high. A pi bond is characterized by the overlapping of two atomic orbitals in a parallel, or “side-by-side” manner, with the overlap being mirror-antisymmetric to a plane passing through one bond axis. It has less overlap, so it is less stable.
3. Valence Shell Electron Repulsion Model (VSEPR)
The configuration of the molecule mainly depends on the mutual repulsion of electron pairs (including bonding electron pairs and lone electron pairs) in the valence electron shell. . The configuration of the molecule is always the one with the least repulsion between the electron pairs.
①If the central atomic valence shell electron pairs are all bonding electron pairs, it is very simple to judge the configuration.
Example of electron logarithmic configuration
2 Linear BeCl2, HgCl2
3 Planar triangle BF3, BCl3
4 Regular tetrahedron CH4, NH4+, CCl4, SiCl4
5 Triangular bipyramidal PCl5, PF3Cl2, SbCl5
6 Regular octahedron SF6, MoF6
②If the central atomic valence shell electron pair contains lone electron pairs, each lone electron pair occupies a corresponding amount of a single bond electron pair. Position (for identical single bond positions, it can be selected arbitrarily, for unequal single bonds, it should be selected according to the principle of the smallest repulsion between electron pairs. For example, in a triangular bipyramid, lone electron pairs are only allowed to occupy any single point in the plane triangle. key position).
③If there is a double bond or triple bond in the molecule, the electron pair repulsion theory still applies, and the double bond is regarded as a single bond. For example, the CO2 molecule is linear O=C=O.
④The repulsive force between the valence electron pair depends on the angle between the electron pair and the bonding condition of the electron pair. The smaller the angle between the electron pairs, the greater the repulsive force. The order of repulsion between electron pairs is lone electron pair-repulsion between lone electron pair>lone electron pair-repulsion between bonding electron pair>bonding electron pair-repulsion between bonding electron pair.
⑤ The count of the number of electron pairs in the valence electron shell of the central atom, that is, the sum of the number of valence electrons of the central atom plus the number of electrons supplied by the ligand is divided by 2. When the oxygen group atoms are used as ligands, it can be considered that they do not provide shared electrons (such as the central atom P of PO43+, 5 valence electrons, plus 3 charges, a total of 8 electrons, that is, 4 pairs of valence electrons), but when the oxygen group When an atom acts as a central atom, it can be considered that it provides 6 valence electrons (for example, the center of SO3 provides 6 valence electrons to S, and oxygen as a ligand does not provide electrons, so the valence electron pair of the central atom S is 3 pairs). If the substance in question is a cation, such as NH4+, the central atom has a total of 5 N valence electrons 2s22p3, plus one electron from each of the four ligands, minus one charge, a total of 8 electrons, that is, 4 pairs of valence electrons.
4. Hybrid orbital theory
The main point is that during the formation of molecules, due to the mutual influence of atoms, different types of atomic orbitals with similar energies are mixed to form a new set of hybrid hybrids with the same energy Orbitals, the number of hybrid orbitals is equal to the number of atomic orbitals that make up the hybrid orbitals; the hybrid orbitals are divided into two types: equal and unequal hybrids; when the hybrid orbitals form a bond, the maximum overlap of the orbitals is required, and the bond and the The repulsion between the keys is minimal.
Sterical configuration example of isotropic hybrid orbital type angle molecules
sp hybrid 1080 linear BtCl3
sp2 hybrid 1200 planar triangular HgCl2
sp3 hybrid 109028/ positive Tetrahedral CH4, SiH4, NH4+
sp3d2 Hybrid 900 and 1800 Regular octahedral SF6
Inequality hybrid orbital type (there are lone pairs of electrons in the hybrid orbital)
Inequality sp3 Hybrid 104045/ Triangular H2O H2S
10705/ Triangular Pyramid NH3 PH3
V. Conjugated Large π Bond and Isoelectronic Principle
(1) pp Large π Bond in Benzene Molecule
In the Lewis structure of benzene, the carbon-carbon bond is divided into single bond and double bond. This structure satisfies the four valence of carbon. However, in fact, I have learned in middle school chemistry that all carbon-carbon bonds of benzene molecules are There is no difference between bond length and bond energy. This contradiction can be solved by the concept that the carbon atoms of the benzene ring form pp large π bonds – the carbon atoms in the benzene molecule take sp2 hybridization, and the three hybrid orbitals are used to form three hybrid orbitals. σ bond, so the bond angle in benzene molecule is 1200.The σ skeleton of the �� plane structure; each carbon atom of the benzene molecule has a p orbital that is not involved in hybridization, which is perpendicular to the molecular plane and parallel to each other. Obviously, there is no difference between the adjacent carbon atoms on the left and right of each carbon atom. It is considered that the electron in the p orbital of a carbon atom that is not involved in hybridization and hybridization only forms a σ bond with one electron in the parallel p orbital of the left adjacent carbon atom. Instead of forming a π bond with the parallel p orbital of the right adjacent carbon atom or the opposite is obviously illogical, it is better to think that all 6 “side by side” parallel p orbitals have a total of 6 electrons together to form a dispersion throughout the benzene ring. pp large pi bond.
(2) pp large π bond in butadiene
The molecular formula of butadiene is H2C=CH-CH=CH2. All 4 carbon atoms are adjacent to 3 atoms, so sp2 heterozygous , these hybrid orbitals overlap each other to form the molecular sigma skeleton, so that all atoms are in the same plane. Each carbon atom also has an uninvolved hybrid p orbital, perpendicular to the molecular plane, with one electron in each p orbital. Therefore, there is a p-p large π bond with “4 orbitals and 4 electrons” in the butadiene molecule. Usually ∏ a b is the symbol of the large π bond, where a represents the number of parallel p orbitals, and b represents the number of electrons in the parallel p orbitals. In addition, CO2 molecules, CO32- and O3 molecules all contain large π bonds.
(3) The principle of isoelectronics
Has the same general formula – AXm, and the molecules or ions with the same total number of valence electrons have the same structural characteristics, this principle is called “the principle of isoelectronics”. Such as: CO2, CNS-, NO2+, N3- have the same general formula – AX2, the total number of valence electrons is 16, and have the same structure – linear molecules, there are no lone pairs of electrons on the central atom and take sp hybrid orbitals to form Linear σ skeleton, the bond angle is 1800, there are two sets of ∏ 4 3 pp large π bonds in the molecule. Similarly, SO2, O3, and NO2- are isoelectronic bodies, and SO42- and PO43- are isoelectronic bodies.
6. Properties of covalent molecules and intermolecular forces
(1) Bond parameters are some physical quantities that characterize the properties of valence bonds, such as bond order, bond energy, bond angle, bond length, bond polarity sex data.
① Bond order = (number of bonding electrons – number of anti-bonding electrons)/2
② Bond energy: For AB-type diatomic molecules, the bond energy is the dissociation energy D.
For polyatomic molecules, bond energy is the average dissociation energy of multiple bonds, such as: N-H bond energy of NH3 molecule
③ Bond length: the equilibrium distance between two nuclei in the molecule.
④ Bond angle: the angle between the bond and the bond in the molecule.
⑤ Bond polarity: Covalent bonds are divided into non-polar covalent bonds and polar covalent bonds, which can be measured by the difference in electronegativity between the two atoms involved in the bond formation. When the electronegativity difference is greater than 1.7, it can be regarded as an ionic bond; when the electronegativity difference is between 1.7 and 0, it can be regarded as a polar covalent bond; when the electronegativity difference is equal to zero, it is a non-polar covalent bond.
(2) Intermolecular forces and hydrogen bonds
1. Molecules can be divided into polar molecules and non-polar molecules. Polar molecules: the centers of gravity of positive and negative charges in the molecule do not overlap; non-polar molecules: the centers of gravity of positive and negative charges in the molecule overlap.
The polarity of a molecule is measured by the dipole moment µ, where µ=o. For non-polar molecules, the larger the µ, the stronger the polarity of the molecule.
µ=q.L
q is the charge on one end of the dipole, and L is the dipole distance of the molecule.
2. The intermolecular force is the van der Waals force, which is one or two orders of magnitude smaller than the chemical bond energy. It includes: ① Orientation force: the interaction force between permanent dipoles. ②Inductive force: the force between the induced dipole and the permanent dipole. ③ Dispersion force: the interaction force due to the instantaneous dipole.
3. Hydrogen bond Hydrogen bond can usually be expressed as X-H…Y, where X, Y represent F, O, N and other atoms with large electronegativity and small atomic radius. X and Y can be the same element or different elements.
Hydrogen bonds have directionality and saturation, and the bond energy is similar to the intermolecular force, which can be divided into two categories:
①Intermolecular hydrogen bonds: such as hydrogen bonds between H2O molecules
② Intramolecular hydrogen bonds: such as the hydrogen bonds in o-nitrophenol:
Chapter 3 Crystal Structure
Chapter Summary: Crystal structure is an important part of chemistry competition questions, because crystal structure can be tested for competition The spatial perception ability of the contestants can test the mathematical skills of the contestants. Therefore, after careful analysis of the chemistry competition questions in recent years, the crystal structure questions have the following forms:
1. Simply examine the three-dimensional structure of a crystal (mainly examine the cubic unit cell). Building the bridge between the micro and macro is Avogadro’s constant.
2. Examining atomic cluster compounds. Competitors are asked to understand what “chemical environment” means. Convex polyhedra often use Euler’s formula.
3. To examine the knowledge of crystal defects. The particles that make up the crystal have non-integer ratios. Learn about ions filling tetrahedral, octahedral, or cubic cavities.
4. Simple crystal structure, but need to establish a mathematical model to answer quickly. For example, mathematically classifying chemical problems according to mathematical knowledgeNa, get the general formula, and then solve the chemical problem according to its general formula.
Trend prediction: In recent years, chemistry competition questions have shown a diversified trend when examining crystal structures. From examining simple crystal structures to examining structural questions that require mathematical models ” and other test questions. Therefore, the author believes that the knowledge depth of crystal structure test questions in the future will show a downward trend, but the ability requirements of the contestants will be higher and higher. That is to examine some questions in special circumstances, breaking old knowledge, building new knowledge and so on.
I. Crystals and Unit Cells (1) The essential feature of a crystal is its “self-normativeness”, that is, the crystal can spontaneously assume the shape of a closed regular convex polyhedron. It is divided into single crystal and double crystal, and some hungry crystalline substances cannot see the regular shape and are polycrystalline. The shapes of single crystals formed under natural conditions are rich and diverse. However, with the help of geometric knowledge, the same crystal planes can be found, and the dihedral angle between the determined crystal planes – “crystal plane angle” is unchanged. . It is called the law of constant angle between crystal planes.
In the microscopic space of the crystal, atoms are regularly arranged regularly. For an ideal perfect crystal, this periodicity is monotonic and invariant, which is a common feature of crystals and is called translational symmetry.
(2) The basic characteristics of the unit cell and the coordinates of the atoms in the unit cell and the counting unit cell have the same apex angle, the same parallel face and the same parallel edge. It is not a unit cell without translation. The geometric features of the parallelepiped can be determined by the relationship of side length and included angle. The side length and included angle of the Bravais unit cell are called unit cell parameters. Usually, the position of atoms in the unit cell is expressed by a triple array composed of x, y, and z in the vector xa+yb+zc, which is called atomic coordinates. The value range of the absolute value of atomic coordinates is 1>∣x(y,z) ∣≥0. A value of 1 is equivalent to a translation to another unit cell, no different from a value of zero.
(3) Elemental unit cell and complex unit cell – body-centered unit cell, face-centered unit cell, bottom-centered unit cell and 14 Bravais lattice types
The unit cell is the description of the crystal microstructure basic unit, but not necessarily the smallest unit. The prime unit cell is the smallest basic unit in the crystal microscopic space, and it cannot be any smaller. The set of atoms in the prime unit cell is equivalent to the smallest set of periodic translation of atoms in the microscopic space of the crystal, which is called a structural unit. The compound unit cell is the polyploid of the prime unit cell; there are three types of split heart unit cell (2-fold), face-centred unit cell (4-fold) and bottom-centre unit cell (2-fold).
(4) Bravais system 7 series and unit cells of prime and complex combination, there are only 14 kinds of unit cells in total, which is called Bravais lattice type in crystallography
2. Types of crystals
br />1. The particles on the lattice nodes in metal crystals are metal atoms or metal ions, and the binding force is metal bonds (free electrons). It is characterized by a large specific gravity, metallic luster, and electrical and thermal conductivity. , has good ductility and so on. The chemical forces between atoms in metal crystals are called metallic bonds. Metallic bonds are a type of delocalized chemical bonds that are spread throughout the crystal. Metal bond theory includes modified covalent bond theory and energy band theory.
2. Ionic crystals The crystals of the ionized species are ionic crystals, such as NaCl, CsCl, and the like. In an ionic crystal, the particles on the lattice nodes are positive and negative ions, and the force between the particles is electrostatic attraction. Crystals are characterized by high melting, boiling point and hardness, but are brittle, have poor ductility, and can conduct electricity in a molten state or in an aqueous solution. When an active metal atom with low electronegativity meets an active non-metallic atom with high electronegativity, positive and negative ions are formed due to electron transfer between atoms, and the chemical bond formed by electrostatic interaction is called ionic bond.
(1) The essence of ionic bond is electrostatic force, without directionality and saturation.
(2) The characteristics of the ion, that is, the charge of the ion, the radius of the ion and the configuration of the electron shell of the ion.
(3) There are the following types of electron shell configurations of ions:
2 Electron configuration: such as Li+, Be2+, ​​etc.
8 electron configuration: such as Na+, Ca2+ and some simple anions Cl-, O2+ and so on.
18 electron configuration: such as Zn 2+, Hg2+, Cu+, Ag+, etc.
18+2 electron configuration: that is, the sub-outer layer 18+ outermost layer 2, such as P2+, Sn2+ and so on.
9~17 Irregular configuration: such as Fe2+, Cr3+, Mn2+, etc.
(4) The strength of ionic bonds is usually measured by the size of the lattice energy U.

U can be calculated by using the Bonn-Haber cycle according to the relevant thermodynamic data,
3. Molecular crystals and atomic crystals such as CO2, HCl, I2, etc. In molecular crystals, the particles on the lattice nodes are molecules (including polar or non-polar), and the force between the particles is van der Waals attraction . There are covalent bonds between atoms in a molecule. Therefore, the melting and boiling points of the crystal are low, the hardness is small, the solid is non-conductive, and it is generally not conductive when it is melted. Only highly polar molecular crystalsA substance (such as HCl) dissolves in water and conducts electricity due to ionization. Such as diamond (C), Si, B, SiO2, SiC, BN, etc., the particles on the lattice nodes of the crystal are atoms, and the atoms are connected by covalent bonds. Therefore, its melting and boiling points are high, its hardness is high, and it is non-conductive and thermally conductive, but Si and SiC have semiconductor properties.
4. Mixed crystals, such as graphite, asbestos, mica, etc., have various forces in their crystals.
Taking graphite as an example, the particles in the layers (ie between C atoms) are bound by covalent bonds, and at the same time, there are free flowing electrons (equivalent to metal bonds), and the layers are connected by van der Waals attraction . Therefore, it has luster, can conduct electricity, conduct heat, and slide easily.
3. Atomic coordinates. The calculation of the number of atoms or molecules in the unit cell and the relationship with the chemical formula
Usually, the three arrays composed of x, y, and z in the vector xa+yb+zc are used to express the position of atoms in the unit cell, which is called atom coordinate. For example, the coordinates of the atoms located at the origin (vertex) of the unit cell are 0, 0, 0; the coordinates of the atoms located at the center of the unit cell are 1/2, 1/2, 1/2; the coordinates of the atoms located at the center of the ab face
The atomic coordinates of ac are 1/2, 1/2, 0; the atomic coordinates at the center of ac are 1/2, 0, 1/2; and so on. The value range of the absolute value of atomic coordinates is 1>|x(y,z)|≥0. A value of 1 is equivalent to shifting to another unit cell, which is no different from a value of 0. For example, the coordinates of the 8 atoms at the corners of the unit cell are all 0, 0, 0. Don’t forget: as long as one vertex of the unit cell has atoms, the other 7 vertexes must also have the same atoms, otherwise the parallelepiped loses translation and is not a unit cell. In the same way, the coordinates of the face-centered atoms of two parallel ab planes are 1/2, 1/2, 0, and one of them must have the other, otherwise it is no longer a unit cell. Conversely, atoms with different coordinates can not be regarded as equivalent courtyards even if they are of the same kind. For example, atoms with coordinates of 0, 1/2, and 1/2 are not equivalent.
4. The relationship between atomic packing and unit cell.

Chapter 4 Chemical Equilibrium
Induction of Match Points: In recent years, the solvated acid-base theory and chemical equilibrium knowledge have been examined many times in the exam questions of chemistry competitions. The main examination questions are:
1. Calculation of chemical equilibrium constants. Including calculation of thermochemical equilibrium constant, calculation of acid-base equilibrium constant, calculation of precipitation-dissolution equilibrium constant, calculation of coordination equilibrium constant, etc.
2. Non-aqueous solvent chemistry. Common non-aqueous solvents are BrF3, N2O4, liquid ammonia, liquid SO2, etc.
Trend prediction: Since the size of the chemical equilibrium constant can measure the feasibility of the reaction to a certain extent, the chemical equilibrium constant is the basis for quantitatively explaining the feasibility of the reaction, and must be a common content of the chemistry competition exam. The non-aqueous solvent is a substance that the contestants are not familiar with. In addition to reacting with many substances, it can also be related to the electrical conductivity of the substance and the ionization of the substance, so it can test the students’ ability to use the knowledge flexibly. The author believes that the above-mentioned competition questions will still appear in the future chemistry competition questions.
1. Chemical Equilibrium
When the reversible reaction proceeds to V positive = V inverse, or from the perspective of chemical thermodynamics, when the reversible reaction proceeds to its free energy change ⊿G=0, it is called chemical equilibrium condition. The chemical equilibrium state is a thermodynamic concept, which refers to a state in which the chemical reaction in the system has neither the spontaneity of the forward direction nor the spontaneity of the reverse direction. Thermodynamics assumes that all chemical reactions are reversible. When the chemical reaction reaches equilibrium, the concentrations or partial pressures of reactants and products no longer change, and the reaction “stagnates”, but this is only apparent, in essence, whatever The forward reaction or the reverse reaction is going on, so the chemical equilibrium is a kind of “dynamic equilibrium”. For example: Dissolution equilibrium, that is, a gas or solid dissolves in water (or other solvent), and finally a saturated solution is formed.
2. Equilibrium constant
1. When any reversible reaction reaches equilibrium at a certain temperature, the equilibrium constant of Aa+bB Dd+Ee
can be expressed as: K=[D]d[ E]e/[A]a[B]b Usually the equilibrium constant of the reversible reaction in solution is expressed by Kc, in this case the equilibrium concentration unit of each substance is mol/l, and the reversible reaction in gas phase is Kp
represents that the concentration of each substance at equilibrium is replaced by partial pressure. The relationship between Kc and Kp for the gas-phase reversible reaction is:

⊿n is the difference between the number of gas molecules before and after the reaction, which is equivalent to (d+e)-(a+b) in the reaction formula.
2. The physical meaning of the equilibrium constant
(1) The equilibrium constant is a characteristic constant of a reaction, which does not change with the initial concentration (or partial pressure) of the substance, but only depends on the nature of the reaction.
(2) The size of the equilibrium constant indicates the degree of the reversible reaction.
(3) The expression of the equilibrium constant indicates the condition for the system to reach equilibrium at a certain temperature.

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