Question

Name an insoluble sulphste of a metal having variable valency​

Answer 1

Since, both zinc and mercury have completely filled d-orbital. So, they tend to lose only 2 electrons from their outermost shell. Hence, only show a valency of +2 and no variable valency. Thus, we can conclude that zinc and mercury do not show variable valency like d-block elements because their d-shells are complete.