Electron Electron ConfigurationsConfigurations

Rules for Housing ElectronsRules for Housing Electrons

Aufbau Principle:Aufbau Principle: an electron occupies an electron occupies the lowest possible energy orbitalthe lowest possible energy orbital(see filling chart) (see filling chart)

Hund’s RuleHund’s Rule1.1. Orbitals of equal energy are occupied by 1eOrbitals of equal energy are occupied by 1e --

before any one orbital is occupied by a 2before any one orbital is occupied by a 2ndnd e e--

2.2. All eAll e- - ’s in singly occupied orbitals must have ’s in singly occupied orbitals must have the same spinthe same spin

Housing RulesHousing Rules

Pauli Exclusion Principle:Pauli Exclusion Principle: no two e no two e- - ’s in ’s in the same atom can have the same set of 4 the same atom can have the same set of 4 quantum numbersquantum numbers

(it’s like an address for finding the e(it’s like an address for finding the e--))

Drawing Orbital DiagramsDrawing Orbital Diagrams

Each orbital is represented by a box or lineEach orbital is represented by a box or line These can be vertical—top to bottom These can be vertical—top to bottom -OR- These can be horizontal –left to right-OR- These can be horizontal –left to right

1 e1 e- - goes in each orbital goes in each orbital ↑↑ or or ↓↓

2 e2 e-- possible in each orbital ↑↓ possible in each orbital ↑↓

Lines are labeled with principle quantum Lines are labeled with principle quantum number and subshell letter (s,p,d,f…)number and subshell letter (s,p,d,f…)

Filling Diagram Filling Diagram

1s

2s

3s

4s

5s

6s

7s

8s

2p2p

3p3p

4p4p

5p5p

6p6p

7p7p

3d

4d

5d

6d

4f

5f

Why do we fill this way?!? …

Relative Energies of OrbitalsRelative Energies of Orbitals

Your Turn! Your Turn!

HeliumHelium He: He:

SiliconSilicon Si: Si:

Writing Electron ConfigurationsWriting Electron Configurations

Eliminates arrows and lines from orbital Eliminates arrows and lines from orbital notationnotation

A superscript is written on the sublevel letter A superscript is written on the sublevel letter to indicate the number of eto indicate the number of e- - ’s’s

Electrons enter lowest energy orbitals firstElectrons enter lowest energy orbitals first(see (see filling chart))

Your Turn! Your Turn!

He:He: 1s1s22 (2 e(2 e- - ’s)’s)

Si:Si: 1s1s222s2s222p2p663s3s223p3p22 (14 e(14 e- - ’s)’s)

Ge:Ge:

MgMg+2+2 : :

Patterns in the Periodic TablePatterns in the Periodic Table

Patterns in the Periodic Table: sPatterns in the Periodic Table: s

  The first two columns in the The first two columns in the P.T. (and He) are known as P.T. (and He) are known as the “s” block the “s” block

Patterns in the Periodic Table: pPatterns in the Periodic Table: p

  Elements 5-10 and Elements 5-10 and all of the elements all of the elements underneath that row underneath that row are known as the “p” are known as the “p” block This block block This block has 6 columns. has 6 columns.

Patterns in the Periodic Table: dPatterns in the Periodic Table: d

Elements 21-30 and all of the elements Elements 21-30 and all of the elements underneath that row are known as the “d” block. underneath that row are known as the “d” block. This block has 10 columns. This block has 10 columns.

Patterns in the Periodic Table: fPatterns in the Periodic Table: f

  The bottom two rows in the P.T. are known as The bottom two rows in the P.T. are known as the f block. This block has 14 columns. the f block. This block has 14 columns.

Valence Electrons Valence Electrons

Valence electrons are the outermost Valence electrons are the outermost electrons of an atom from the s and p electrons of an atom from the s and p orbitalsorbitals

Atoms with a complete shell of valence Atoms with a complete shell of valence electrons (selectrons (s22pp66) are considered chemically ) are considered chemically inertinert

Electron ConfigurationsElectron Configurations

Noble Gas ShorthandNoble Gas Shorthand For elements with completely filled shellsFor elements with completely filled shells Substitute [noble gas] for electron Substitute [noble gas] for electron

configuration notationconfiguration notation

Example:Example:

Si: 1sSi: 1s222s2s222p2p663s3s223p3p22 can be written [Ne]3s can be written [Ne]3s223p3p22

Valence ElectronsValence Electrons

For most elements, valence electrons can For most elements, valence electrons can be defined as those in the electronic shell be defined as those in the electronic shell of highest principle NRG level (n) of highest principle NRG level (n)

Ex. the electron configuration of Ex. the electron configuration of phosphorus (P) is 1sphosphorus (P) is 1s22 2s 2s22 2p 2p66 33ss22 33pp33 so so that are 5 valence electrons (3sthat are 5 valence electrons (3s22 3p 3p33),),

Valence ElectronsValence Electrons

Electron Dot Diagram Electron Dot Diagram

Shows the number of Shows the number of valence electrons valence electrons

The first column of the The first column of the Periodic Table have Periodic Table have electron configurations electron configurations that end in sthat end in s11 so they so they have one valence have one valence electron. electron.

Electron Dot DiagramElectron Dot Diagram

The second column The second column of the Periodic Table of the Periodic Table (and He) have (and He) have electron electron configurations that configurations that end in send in s22 so they so they have two valence have two valence electrons. electrons.

Electron Dot Diagram Electron Dot Diagram

The column starting The column starting with Boron has with Boron has electron electron configurations that configurations that end in send in s22 p p11 so they so they have three valence have three valence electrons. electrons.

Electron Dot DiagramElectron Dot Diagram

The column starting The column starting with Carbon has with Carbon has electron electron configurations that configurations that end in send in s22 p p22 so they so they have four valence have four valence electrons. electrons.

Electron Dot Diagram Electron Dot Diagram

The column starting The column starting with Nitrogen has with Nitrogen has electron electron configurations that configurations that end in send in s22 p p33 so they so they have five valence have five valence electrons. electrons.

And the pattern continues…

Electron Dot DiagramElectron Dot Diagram

Electron ConfigurationsElectron Configurations

Exceptions (rows 4 & 5 of P.T.)Exceptions (rows 4 & 5 of P.T.) Half filled orbitals have special stability (all Half filled orbitals have special stability (all

electrons have the same spin)electrons have the same spin)

Cr: [Ar] 4sCr: [Ar] 4s113d3d55 NOT… [Ar]4s NOT… [Ar]4s223d3d44

Filled orbitals have special stabilityFilled orbitals have special stability

Pd: [Kr] 4dPd: [Kr] 4d1010 NOT… [Kr] 4d NOT… [Kr] 4d885s5s22