Here's why:

* Chemical Formula: The chemical formula for bisulphite is HSO₃⁻.

* Structure: The bisulphite ion has one hydrogen atom, one sulfur atom, and three oxygen atoms. The sulfur atom is bonded to three oxygen atoms, and one hydrogen atom is attached to one of the oxygen atoms.

* Charge: The ion carries a negative charge of -1. This is due to the sulfur atom having a formal charge of +2, and the oxygen atoms having a formal charge of -1 each.

Therefore, the valency of bisulphite is -1, meaning it can form one bond with a positively charged ion.