Question

The element which shows variable valency is iron/sodium/aluminum

Answer 1

Element which shows variable valency is - iron.

•Iron is a transition element, with atomic number 26.

•Electronic configuration of iron is [Ar] 3d6 4s2.

•Variable valency of iron is +2 and +3.

•This happens, because iron can lose two electrons from 4s orbitals, which will make it stable.

•Iron can also go another way, using principle that half filled orbitals are more stable.

•Thus, it can also lose three electrons from 3s, leaving each electron unpaired. This leads to +3 valency.

Answer 2

Iron shows variable valency

Explanation:

Iron is a transition metal that share outer electronic configuration meaning the 4s orbitals are same but the 3d orbitals change among the these metals.Theses orbits are close to the energy so iron gives up 2 outer 4s electrons, and sometimes it gives up inner 3d electrons resulting in having either positive 2 or 3 charges.