Question

Although + 3 oxidation states is the characteristic oxidation state of lanthanoids but cerium shows + 4 oxidation state also. Why?

Answer 1

Electronic configuration of Ce : [Xe] 4f^d 5d¹ 6s². Generally 5d¹ and 6s² electrons are lost by the lanthanoids in their reactions i.e., they exhibit +3 oxidation states. But Ce exhibit + 4 oxidation state also because it gains extra stability by losing 4f¹ electron because it will give rise to completely filled orbitals.