Question

what is variable valency.

Answer 1

certain element combined with other atoms donating,accepting or sharing electron in different proportion depending on the nature of reaction .

Answer 2

variable valency is property of atom of an element to exhibit more than one valency
It is generally exhibited by elements of d block in the periodic table
This occurs because electrons from anti penultimate shell may get excited to the last shell due to overcrowding and achieve stability and achieve low charge density