First 20 Elements and atomic number

Hydrogen

1

Neon

10

Sodium

11

Magnesium

12

Aluminium

13

Silicon

14

Phosphorus

15

Sulfur

16

Chlorine

17

Argon

18

Potassium

19

Helium

2

Calcium

20

Lithium

3

Beryllium

4

Boron

5

Carbon

6

Nitrogen

7

Oxygen

8

Fluorine

9