The chemical formula of the phosphide of element X is
X₃P
How can you write the chemical formula of its phosphide?
When an element X has a valency of 1, it means it can form only one bond with another atom. In the case of a phosphide, it would bond with a phosphorus atom, which has a valency of 3.
To balance the charges and satisfy the valencies, we need three of element X to bond with one phosphorus atom. Therefore, the chemical formula of the phosphide of element X would be:
X₃P
This formula indicates that three atoms of element X (represented by X) are bonded to one phosphorus atom (represented by P).