1
Hydrogen
H
2
Helium
He
3
Lithium
Li
4
Beryllium
Be
5
Boron
B
6
Carbon
C
7
Nitrogen
N
8
Oxygen
O
9
Fluorine
F
10
Neon
Ne
11
Sodium
Na
12
Magnesium
Mg
13
Aluminium
Al
14
Silicon
Si
15
Phosphorus
P
16
Sulphur
S
17
Chlorine
Cl
18
Argon
Ar
19
Potassium
K
20
Calcium
Ca