• The energy levels are called Principle Energy Levels
  • The principal energy levels contain sub-levels. Each principal energy contains a different number of sub-levels.

Principal Energy Level

Number of Sub-levels

1

1 (S)

2

2 (S,P)

3

3 (S,P,D)

4

4 (S,P,D,F)

Sub-level

Max number of Electrons

S

2

P

6

D

10

F

14

Principal Energy Level, n

Sub-level

Max Number of Electrons

1

1s

2

2

2s,2p

8

3

3s,3p,3f

18

4

4s,4p,4d,4f

31

e.g.

  1. a) Sodium = S block
  2. b) Iron = D block
  3. c) Sulphur = P block
  4. d) Chlorine = P block
  5. c) Radium = S block
  6. e) Neon = P block

Electron Configurations

Element

Electron Configuration

Hydrogen

1s1

Helium

1s2

Lithium

1s1, 2s1

Beryllium

1s1, 2ss

Boron

1s1, 2ss,2p

Carbon

1s1, 2ss,2p2

Neon

1s1, 2ss,2p3

Oxygen

1s1, 2ss,2p4

Fluorine

1s1, 2ss,2p5

Neon

1s1, 2ss,2p6

Sodium

1s1, 2ss,2p6, 3s