Question

how are elements having Variable valency named with example

Answer 1

Fe 3+ Ferrate
Fe 2+ Ferrous

Answer 2

Explanation:

Valency is defined as the bonding capacity of an element. For instance, the Hydrogen valence electron is 1 because it has 1 electron in its outermost shell. It needs 1 electron to become stable. There are many elements that exhibit different valences i.e., their bonding capacity varies. These elements have more than one specific valency.

For example, iron is a metal that exhibits different valences. It exhibits valences of 2+ and 3+. The number of electrons in iron is 26. Like other metals, it has 2 electrons in the 4s orbital and 4 in the 4d orbital. It loses 2 electrons from 4s orbital to attain stability making its valency as 2+. In the d orbital, which is more stable, and it loses another electron from the d electron making its valency as 3+.

So, iron exhibits $Fe^{2+}$ or ferrous state and also $Fe^{3+}$ or ferrate state.