Electron Configuration Notation with Atomic Structure Review

Chemistry IMr. Streeter

Bohr’s Atom Model

-Confines electrons in shells-Electrons loses energy due to movement.-Electrons can be in certain levels depending of the energy they have.-The region where we can find the electron with high probability is called the orbital.

Nature of the electron

-Thompson’s work show that e- behave like particles.-In 1924, Louis de Broglie states that e- behave like waves based on Bohr’s model.-This was explained in the electromagnetic spectrum.

The frequency is mathematically related to the wavelength:c=λv

Where c=speed of light (3.0 x 108 m/s)λ= wavelength v= frequency

Electromagnetic Spectrum

Electromagnetic Spectrum

All the frequencies or wavelenghts of electric radiation.

Electromagnetic Spectrum

-The movement of electrons produced light when received and release energy.-In 1905, Albert Einstein proposed that light have properties of light and waves.

Light Emission

Light Emission

Electron in lowest possible energy is in ground state.

Electron that gains energy move to excited state.

Electron release energy as go back to ground state.

Light Emission

E1=Energy in ground state E2=Energy in excited stated. Overall energy= E1-E2

Quantum Numbers

-Number that specifies the properties of the electrons.

-There are 4 quantum numbers: n, , m and ms

n= level number (n=1 thru 7). (n-1)= Shape and type of orbital

s=0p=1d=2f= 3

m (from – ,0,+)=Magnetic quantum numberms= Magnetic spin. Only have two possible numbers (+1/2 and -1/2)

Quantum Numbers

Electron configurations

-Arrangements of electrons in an atom.-Each orbital can have only 2 electrons and with different quantum numbers. This is known as Pauli exclusion principle.

Electron configuration

Types and shapes of orbitals

Electron configuration

Aufbau principle -Electron fill lowest energy levels first.

Ex. 1s<2s<2p<3s<3p

Electron configuration

NotationsThere are 3 notations:1) Long notation or electron

configuration1s22s22p6

2) Orbital Notation

s1

s2

Electron configuration

3) Shorthand Notation or Noble Gas configuration.

[Ne]3s23p4

Electron configuration

Hund’s Rule -For atoms in ground state, the number of unpaired electrons is the maximum possible and have the same spin.

Order in which subshells are filled with electrons

1s

2s

3s

4s

5s

6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

Electron configuration

Example What is the electron configuration of

an element with atomic number of 9 (Z=9)

An element with z=9 is Fluorine.We start with the less energy level and

orbital, so then is 1s22s22p5. The orbital notation will be then

pss 221

Filling Rules for Electron Orbitals

Aufbau Principle: Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for.Pauli Exclusion Principle: An orbital can hold a maximum of two electrons. To occupy the same orbital, two electrons must spin in opposite directions.Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum number of unpaired electrons results.

*Aufbau is German for “building up”

General Rules

Pauli Exclusion Principle Each orbital can hold TWO electrons

with opposite spins.

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

General Rules

Aufbau Principle Electrons fill the

lowest energy orbitals first.

“Lazy Tenant Rule”

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

2s

3s

4s

5s

6s

7s

1s

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

1s

2s

2p

3s

3p

4s

4p

3d

4d5s

5p6s

7s

6p

6d

4f

5f

5d

Energ

y

RIGHTWRONG

General Rules Hund’s Rule

Within a sublevel, place one electron per orbital before pairing them.

“Empty Bus Seat Rule”

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

O 8e-

Orbital Diagram

• Electron Configuration

1s2 2s2

2p4

Notation

1s 2s 2p

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

O15.9994

8

• Shorthand Configuration

S

16e-Valence ElectronsCore Electrons

S 16e- [Ne] 3s2 3p4

1s22s22p63s23p4

Notation

Longhand Configuration

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

S32.066

16