Electronic configuration

1
Electronic configuration

• One shell at a time

2
How many electrons

• In an atom there are as many electrons as there
  are proton

• Hydrogen, atomic number 1
• ? 1 proton ? 1 electron

• Iron, Atomic number 26
• ? 26 protons ? 26 electrons

3
Shells

• The electrons are organised in concentric SHELLS,
  or layers

Etc
4
Filling the shells

• Each shell can only contain a certain number of
  electrons

Shell
1 Contains up to 2 electrons
2 Contains up to 8 electrons
3 Contains up to 8 electrons
4 Contains up to 18 electrons
5
Hydrogen atom
H
1
1
X
so one electron
X
6
Lithium atom
Li
2
, 1
X
3
X
X
so three electrons
X X X
7
Carbon atom
C
2
, 4
X
X
6
X
X
so six electrons
X X X X X X
X
X
8
Sodium atom
X
Na
2
, 8
, 1
X
X
11
X
X
X
X
X
X
so eleven electrons
X X X X X X X X X X X
X
X
9
Sodium atom
X
2
, 8
, 1
X
X
Electronic Structure (written)
X
X
X
X
X
X
X
X
Electronic Structure (drawn)
10
Helium atom
so electrons
11
Phosphorus atom
so electrons
12
Neon atom
so electrons
13
Calcium atom
so electrons
14
Key points to remember

• How many electrons in an atom
• How many electrons per shell
• Drawing the electronic structure
• Writing the electronic structure