Electron configuration

ELECTRON CONFIGURATION Periodic Table

s, p, d, and f ORBITALS

S- Orbital

P - orbitals

D- orbitals

F-orbitals

QUANTUM NUMBERS

• Principal Quantum Number, n

• Azimuthal Quantum Number, l

• Magnetic Quantum Number, ml

Exercise

• What are the similarities and differences between the hydrogen atom 1s and 2s orbitals?

• For n=4 what are the possible values of l and m?

• give the values for n, l, m fora. 2pb. 5dc. 5f

Main Energy Level

No. of Sublevel

Identity of

Sublevels

No. of Orbitals

(n2)

Max. No. of

Electrons(2n2)

1 1 1s 1 2

2 22s2p

13

26

3 33s3p3d

135

2610

4 4

4s4p4d4f

1357

261014

HOW DO THE ELECTRONS POPULATE THE AVAILABLE ORBITALS?

Electron Spin Quantum Number, m• Two possible values are allowed

+ ½ and - ½

• Opposite directions

Can two electrons in an atom have the same set of quantum numbers?

NO

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.

Electron Configuration

• The way in which electrons are distributed among the various orbitals of an atom

Aufbau Principle

• Electrons occupy orbitals of lower energy first.

The relation between orbital filling and the periodic table

The relation between orbital filling and the periodic table

Hund’s Rule

• For degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized.

Orbital Diagram

Anomalous Electron Configuration

Example:Chromium

Copper

• Consequence of the closeness of the 3d and 4s orbital energies.

• Minor departures from the expected

• Not of great chemical significance

Seat work

Write the electron configuration and the electron orbital diagram for the following elements.

1. Cl2. Os3. Cs