Question

Why +3 is the most stable oxidation state of lanthanoids?

Answer 1

Because by loosing 3 electrons most of the lanthanoid elements get stable configuration of f0,f7 and f14.

Answer 2

Answer:

In the case of lanthanoids , +3 oxidation state is most common.

That is, Ln(III) compounds are predominant.

However, +2 and +4 oxidation states can also be found in the solution or in solid compounds