6.7 thru 6.9 narrated notes

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Chapter 6 – Part 4 : 

Chapter 6 – Part 4 6.7 Orbitals in Many-Electron Atoms 6.8 Electron Configurations 6.9 Electron Configurations and the Periodic Table

Many Electron Atoms : 

In a many electron atom, for a given value of n, the energy of an orbital increase with increasing value of l Arrange the n = 4 orbitals in order of increasing energy 4s, 4p, 4d, 4f 6.7 Many Electron Atoms

Degenerate Orbitals : 

Degenerate – A situation in which two or more orbitals have the same energy The 2px, 2py, and 2pz orbitals are degenerate 6.7 Degenerate Orbitals

Electron Spin : 

A property of the electron that makes it behave as though it were a tiny magnet. The electron behaves as if it were spinning on its axis; electron spin is quantized 6.7 Electron Spin

Electron Spin : 

The fourth quantum number - spin magnetic quantum number, ms The two possible values are + ½ and – ½ and indicate the direction in which the electron is spinning 6.7 Electron Spin

Pauli Exclusion Principle : 

No two electrons in an atom can have the same set of four quantum numbers n, l, ml, and ms An orbital can hold a maximum of two electrons and they must have opposite spins 6.7 Pauli Exclusion Principle

Electron Configuration : 

The way in which the electrons are distributed among the various orbitals of an atom is called the electron configuration of the atom 6.8 Electron Configuration

Electron Configuration : 

The most stable electron configuration of an atom is that in which the electrons are in the lowest possible energy states The orbitals are filled in order of increasing energy, with no more than 2 electrons per orbital 6.8 Electron Configuration

Write the orbital diagram for nitrogen : 

N Atomic number = 7 7 protons, 7 electrons 1s 2s 2p Identify the paired and unpaired electrons for nitrogen. Teal electrons are paired and orange electrons are unpaired 6.8 Write the orbital diagram for nitrogen

Hund’s Rule : 

Hund's rule states that for degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized Spin all up and unpaired then when paired, spin down 6.8 Hund’s Rule

Practice Exercise : 

Write the electron configuration of phosphorus. P (atomic number = 15) 15 protons and 15 electrons 1s22s22p63s23p3 How many unpaired electrons does a phosphorus atom possess? Three unpaired elctrons 6.8 Practice Exercise

Condensed Electron Configurations : 

Explain how to write the condensed electron configuration of an element. Use the nearest noble-gas element of lower atomic number in brackets Add on any additional electrons 6.8 Condensed Electron Configurations

Valence Electrons : 

The outermost electrons of an atom; those that occupy orbitals not occupied in the nearest noble-gas element of lower atomic number 6.8 Valence Electrons

Electron Configurations and the Periodic Table : 

The periodic table is structured so that elements with the same pattern of outer shell electron configuration are arranged in columns 6.9 Electron Configurations and the Periodic Table

Slide 15: 

6.9

Practice Exercise : 

Which family is characterized by an ns2np2 electron configuration in the outermost occupied shell? Group 4A 6.9 Practice Exercise

Practice Exercise : 

Use the periodic table to write the condensed electron configurations for Co [Ar]3d74s2 Te [Kr]4d105s25p4 6.9 Practice Exercise

Electron Configurations : 

For representative elements, we do NOT consider completely full d or fsubshells to be among valence electrons Explain the above statements using Sn as an example Sn = [Kr]5s24d105p2 = 4 valence electrons 6.9 Electron Configurations

Electron Configurations : 

For transition elements, we do NOT consider a completely full fsubshell to be among the valence electrons. Explain the above statement using W as an example. W = [Xe]6s25d4 = 2 valence electrons 6.9 Electron Configurations