Certain elements exhibit more than one valency, that means they show variable valency.
Ferrous is written as Iron (II) and Ferric is written as Iron (III).
| Metal | Radicals | Radicals Valency |
| Iron | Ferrous [Iron (II)]Ferric [Iron (III)] | 23 |
| Copper | Cuprous [Copper (I)]Cupric [Copper (II)] | 12 |
