What is the valence of an element or radical?

Valency is the charge of an ion or radical which has either lost or gained electrons

Note that metals lose electrons easily to become positive ions. This is why most metals are good conductors of electricity.

A Radical is a group of atoms usually charged which can keep itself intact and behaves like a unit in a chemical reaction.

For example:hydroxide ion (OH-) and ammonium ion (NH4+).

When A compound contains more than one such radicals then the formula of this is taken in brackets with their number written on the lower right hand side.