Question

Define valency. Give 2 examples for non metallic element and polyatomic ion

Answer 1

number of elctrons present in outermost shell is called valency
non mettallic elements are
1)oxygen
2)sulfur
3)nitrogen
and polyatomic ions are
1)hydroxide 2)phosphate

Answer 2

Valency is the combining capacity of an atom or of a radical.

Examples of non metallic elements:
Chlorine and Hydrogen
 
Examples of polyatomic ions:
Hydrogen carbonate and Hydrogen sulphate.