1. ELECTRON CONFIGURATION

2. LABEL THE SUBLEVELS (1 S, 2 S, …)

3. PRACTICE 1 Sulfur ( ______ electrons) Electron configuration: a. How many E.L. in an atom of S have e - ? b. How many e - are in the 2 nd energy level?

4. PRACTICE 1 ANSWER Sulfur ( __16____ electrons) Electron configuration: 1s 2 2s 2 2p 6 3s 2 3p 4 a. How many E.L. in an atom of S have e - ? Three b. How many e - are in the 2 nd energy level? 8 (2+6 - just add the superscripts)

5. PRACTICE 2 Iron (________ electrons) Electron Configuration: a.How many E.L. in an atom of Fe contain e - ? b.b. How many e - in 3 rd energy level?

6. PRACTICE 2 ANSWER Iron (___26_____ electrons) Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 a. How many E.L. in an atom of Fe contain e - ? Four b. How many e - in 3 rd energy level? 14 (2+6+6)

7. NOBLE GAS NOTATION (“SHORT HAND”) This is used to represent electron configurations of noble gases using bracketed symbols.

8. SHORT HAND PRACTICE Use shortcut method to write e-configurations for Ar and P. Ar: P: [Ne] 3s 2 3p 6 or [Ar] [Ne] 3s 2 3p 3

9. GROUND STATE VS EXCITED STATE Ground State – The most stable, lower energy arrangement of the electrons in an atom. (The electrons are in the correct order of orbitals.) Excited State – When atom gains energy the electrons jump into higher energy level. Example: Identify the following atoms and describe their state. (Ground or Excited) a.1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 4p 3 b.1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 c.1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 8

10. ELECTRON CONFIGURATION A. Aufbau Principle – Electrons enter orbitals of lower energy first. 1s 2, 2s 2, 2p 6, 3s 2, 3p 6, 4s 2, 3d 10, 4p 6, 5s 2, 4d 10, 5p 6, 6s 2, 4f 14, 5d 10, 6p 6, 7s 2, 5f 14, 6d 10, 7p 6 (or use PT) B. Pauli Exclusion Principle – No more than __2______ electrons can occupy the same orbital AND they must spin in opposite directions. (Opposite spins help hold e - in an orbital by creating magnetic attraction.) C. Hund’s Rule – Orbitals of equal energy must EACH have _1____ electron with the same ____spin______ before any orbital is occupied by a 2 nd electron.

11. ELECTRON CONFIGURATION