Question

What is the formal charge on the chlorine atom in the chlorate ion?

Answer 1

Chlorate ion is ClO3⁻

x- charge of Cl,
every oxygen atom here has charge = -2,
whole ion has charge =-1.
So we can write
x+3*(-2)=-1
x-6=-1
x=+5
So the charge of chlorine =+5.