Answer 1

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	Valency
Iron	Ferrous [Iron (II)] Ferric [Iron (III)]	2 3
Copper	Cuprous [Copper (I)] Cupric [Copper (II)]	1 2