Question

What is the 1st 20 elements of the periodic table , write their valencies , atomic mass no. and atomic no.

Answer 1

Answer:

Atomic Number Element Symbol

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 Sulfur S

17 Chlorine Cl

18 Argon Ar

19 Potassium K

20 Calcium Ca