Question

Why cerium forms tetrapositive ion in aqueous solution?

Answer 1

Ce is one of the lanthanoids. Lanthanoids have two oxidation states +2 and +4.

But in Case of Cerium +4 is more stable oxidation state.

Atomic No. of Ce = 58

Electronic Configuration : [Xe] $4f^{1}\: 5d^{1}\: 6s^{2}$

Cerium loses all four electrons easily to aquire a stable electronic configuration of [Xe] or Xenon.

Since Cerium ion($Ce^{4+}$) is small in size it has high Hydration energy.