1_atom_structure 2015.ppt
- Количество слайдов: 23
Chemistry Lections: 18 h Labs: 18 h Oksana Shkriblyak Ivano-Frankivsk 2015
Plane Basic Concepts : Atoms, Molecules, Chemical Reaction Atom structure : isotops, isobars Electron configuration Periodic Law, main correlation Conclusions
Basic terms & concepts in chemistry Atom The atom is a basic unit of matter that consists of a dense central Nucleus surrounded by a cloud of negatively charged electrons. Molecule A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Mixtures and pure substances Graphene photo taken by TEAM@Berkeley Lab Transmission Electron Aberration-Corrected Microscope
4 Chemical reactions Chemical reaction A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Can be observed by: heating, light, color change, odor, formation of residue or gas.
5 Elements Chemical element A chemical element is a substance that contains only one type of atom. Gold Carbon (diamond) Fluorine
6 Rutherford experiment and atom model A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. 4 4 5 Ernest Rutherford, 1871– 1937; UK Nobel prize @1908 1 2 3 3 6
Atom model Rutherford interpreted the gold foil experiment as suggesting that the Positive charge of a heavy gold atom and most of its mass was concentrated in a nucleus at the center of the atom— the Rutherford mode 7 Isotopes are variants of a particular chemical element such that, while all isotopes of a given element share the same number of protons in each atom, they differ in neutron numbers. Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons. An example : 40 S, 40 Cl, 40 Ar, 40 K, and 40 Ca.
8 Atom structure Symbol Relative charge Mass -1 Electron A (Mass number) ≈5. 4· 10 -3 Z (Charge) Proton +1 ≈1, 00 Neutron 0 ≈1, 00 Isobars Isotopes (6 p, 6 n) (1 p, 0 n) A = Z + N N (Neutrons) Calculation example (20 p, 20 n) A = Z + N (6 p, 7 n) (1 p, 1 n) (19 p, 21 n) 16 = 8 + N => N=8
Born atom model 9 Hydrogen spectra Niels Bohr 1885 -1962 Danish, UK Nobel prizze @ 1922 The emission spectrum of atomic hydrogen is divided into a number of spectral series The Bohr model of the hydrogen atom. A negatively charged electron confined to an atomic shell orbits a small, positively charged atomic nucleus and a quantum jump between orbits is accompanied by an emitted or absorbed amount of electromagnetic radiation.
10 Born postulates Postulates 1. Electrons orbit the nucleus. they are held in orbit by an electrostatic force. Niels Bohr 1885 -1962 Danish, UK Nobel prizze @ 1922 2. Electrons can only be in certain, permitted orbits and an electron does not emit radiation when it is in one of these orbits. The Bohr model of the hydrogen atom. A negatively charged electron confined to an atomic shell orbits a small, positively charged atomic nucleus and a quantum jump between orbits is accompanied by an emitted or absorbed amount of electromagnetic radiation. 3. An electron only emits radiation when it "falls" from a higher energy state to a lower state. 4. The radii of the allowed orbits are also quantized - each energy state has a specific radius proportional to h/2π.
11 Quantum numbers Each electron orbit can be described by set of atom numbers Symbol n principal number quantum shell l azimuthal number quantum Subshell (shape) m magnetic number s quantum spin projection quantum number Orientation of sub shell in space spin of the electron from 1 to ∞ from 1 to n-1 form -1 to +l -1/2 or+l/2
12 Quantum numbers n l principal quantum number; Correspond to the electron shell from 1 to ∞ Azimuthal quantum number; Define orbital shape and can be form 0 to n-1 s (l=0) p (l=1) d (l=2) f (l=3)
13 Quantum numbers Energy minimum The Pauli exclusion principle Hund's rules A maximum of two electrons are put into orbitals in the order of increasing orbital energy: the lowest-energy orbitals are filled before electrons are placed in higherenergy orbitals. The Pauli exclusion principle refers to the fact that certain particles cannot be at the same place at the same time, with the same energy. For a given electron configuration, the term with maximum multiplicity has the lowest energy. N=2 n 2 wrong The Aufbau principle right Orbitals are filled in the order of increasing n+l; Where two orbitals have the same value of n+l, they are filled in order of increasing n.
Energy levels 14 Energy minimum 1 s, 2 p, 3 s, 3 p, 4 s, 3 d, 4 p, 5 s, 4 d, 5 p, 6 s, 4 f, 5 d, 6 p, 7 s, 5 f, 6 d, 7 p, ……. In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. [1] For example, the electron configuration of the neon atom is 1 s 2 2 p 6.
15 Energy levels Example: 1 Н І period, 1 s 1 3 Lі ІІ period, 1 s 22 s 1 17 Cl ІІІ period, VII група, 1 s 22 p 63 s 23 p 5 2 2 6 2 3 23 V ІV period, 1 s 2 s 2 p 3 s 3 p 4 s 3 d 2 2 6 10 2 6 2 38 Sr V period, 1 s 2 s 2 p 3 s 3 p 3 d 4 s 4 p 5 s Lа VІ period, 1 s 22 p 63 s 23 p 64 s 23 d 104 p 65 s 24 d 105 p 66 s 25 d 1 57 ↑↓ ↑ ↑ Graphical formula of the oxygen atom : ↑↓ 2 р 22 s 22 p 4 ↑↓ 2 s 8 О ІІ period, VI group, 1 s 1 s
Electron configuration vs. chemical reactivity 16 Chemical activity of the element is a function electron configuration. Especially important is outer shells. The ionization energy of an atom or molecule describes the amount of energy required to remove an electron from the atom or molecule in the gaseous state. X → X+ + e. Electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion X + e- → X-
Electron configuration vs. chemical reactivity 17 Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom or a functional group to attract electrons (or electron density) towards itself Metal Beryllium : 1. 57 Nonmetal Sulfur : 2. 58
Periodic law of Mendeleyev Chemical properties of the element it’s compound is in periodic dependency of atom number (or atom charge) 1834 -1907 Russian chemist 18
Main correlation for the properties in the table 19
Chemical properties base on element position Element Ca Electron formula Position 4 -th period; 2 -nd group 20 Properties Full: 1 s 22 p 63 s 23 p 64 s 2 Short: 4 s 2 Graphical : 1 ↑↓ 2 ↑↓ ↑↓ 3 ↑↓ ↑↓ 4 Common metal with metallic color, react with acid, and demonstrate other common behavior ↑↓ Ca under N 2 atmosphere
Chemical properties base on element position Element O Electron formula Position 6 -th period; 2 -nd group Properties Full: 1 s 22 p 4 Short: 2 p 4 Graphical : 1 ↑↓ Oxygen – typical non metall. Form oxides, react with metals ↑↓ 2 21 ↑↓ ↑ ↑ Liquid oxygen, bp. -182 C 0
Must to remember: ATOM is composed of neutrons, protons and electrons Electron configuration is in strong correlation with it’s chemical properties
Please, be prepared for the test Questions for the test : Calculate : protons, neutrons, and electrons for certain element Isotopes, and Isobars : be able to reveal and provide with examples Electron configuration : be able to write it down for each element Periodic law : main correlation based on the table, it’s connection with electronic configuration
1_atom_structure 2015.ppt