Question

formula of carbonate of the metal M is M2CO3 . write the formula of its chloride...

Answer 1

Valency of M=3 (On crossing over valencies)
So clearly, formula of its chloride=MCl3 (As valency of M is 3 & valency of Cl is 1)

Answer 2

M₂CO₃
Valency of carbonate ion (CO₃²⁻) is 2
There are 2 metal atoms in given molecule
∴ Valency of metal (M) is 1

So, it’s chloride will be MCl

E.g. If M is taken as Sodium metal then,
Valency of sodium is 1
Sodium carbonate: Na₂CO₃
Sodium chloride: NaCl