Electron Arrangement Another link for review S/28Elec-config.pdf 1

Quantum Numbers Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals. This is also known as probable location of electrons about the nucleus of an atom. 2

Principal Quantum Number, n Indicates the main energy level occupied by an electron (n=1,2,3,…7) 3

Angular momentum quantum number has 4 basic shapes The values and shapes are l = 0s shape l = 1p l = 2d l = 3f 4

Angular Momentum Quantum Number, l s shape sparknotes.com 5

p shape 6

d shaped orbitals Courtesy of bluelight.ru 7

f orbitals f orbitals are very complex and you will not be responsible for drawing them. The site below has more informtion. AOs/ao4.html 8

Spin quantum number, s, has only two possible values Has only two possible values: +1/2, -1/2. See table 2 on page 110 to get a better idea of the number of orbitals and electrons per energy level. 9

Electron Configurations I.Rules Governing Electron Configurations II.Orbital Notation III.Electron-Configuration Nottion 10

Rules Governing Electron Configurations I.Aufbrau Principle – an electron occupies the lowest-energy orbital that can receive it. Source: This is really a thought process in which we think about building up an atom from the one that preceeds it in atomic number, by adding a proton and neutrons to the nucleus and one electron to the appropriate atomic orbital. 11

II. Pauli Exclusion Principle – no two electrons in the same atom can have the same set of four quantum numbers. Rules Governing Electron Configurations, cont. The box at left shows the different spin states of two electrons in the same orbital. This drawing is the electron configuration of a helium atom’s 1 s orbital. 12

Rules Governing Electron Configurations, cont. III.Hund’s Rule – orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin state. en.citizendium.org 13

Source: chem.wisc.edu Periodic Table: Orbitals 14

Orbital Notation Source: naturalphilosophers.org Pair of electrons in an orbital Unpaired electron Orbital name What element is this showing? Fluorine 15

Sample problems Write the electron configuration notation for Silicon and Scandium (use the Aufbrau diagram) Si has 14 electrons 2 in 1s 2 in 2s 6 in 2p 2 in 3s 2 in 3p written as: 1s 2 2s 2 2p 6 3s 2 3p 2 16

Scandium Electron Configuration Notation Sc has 21 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 17

Scandium Notations Electron Configuration Notation 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 Orbital Notation __ __ __ __ __ __ __ __ __ __ __ __ __ __ ___ 1s 2s 2p 3s 3p 4s 3d 18

Notations,cont. Noble gas notation – back up to the last noble gas prior to the element and add orbitals: [Ar}4s 2 3d 1 Dot notation - shows only the outer shell electrons for an element’s atom (maximum number of e’s in an outer shell is 8) for Sc: 4s 2 for F: 2s 2 2p 5 for Ne: 2s 2 2p Sc : : F : : Ne :... Other info: atoms are more stable when they have a half- filled or completely filled outer shell 19

Remaining Ch5 asgns. From book 137/1-3; 149/1-5; 165/ /1-15 (use periodic chart) 166/17a-c,18a-c,19c-e,20,21a-c 167/24-29,32,34 167/