Question

valancy of first 20 elements​

Answer 1

depends on amount of electron present in last shell of atom

Answer 2

Hydrogen- +1
Helium- 0
Lithium - +1
Beryllium - +2
Boron- +3
Carbon-4
Nitrogen- -3
Oxygen- -2
Fluorine - -1
Neon- 0
Sodium- +1
Magnesium -+2
Aluminium -+3
Silicon-4
Phosphorus- -3
Sulphur- -2
Chlorine- -1
Argon- 0
Potassium- +1
Calcium- +2