Question

Name the members of the lanthanoid series which exhibit $+4$ oxidation states and those which exhibit $+2$ oxidation states. Try to correlate this type of behaviour with the electronic configurations of these elements.

Answer 1

$Ce(Z=58),Pr(Z=59),Nd(Z=60),Tb(Z=65)$ and $Dy(Z=66)$ shows +4 oxidation state. They acquire electronic configuration closer to $4f^0$ and $4f^7$.

$Nd(Z=60),Sm(Z=62),Eu(Z=63),Tm(Z=69)$ and $Yb(Z=70)$ shows $+2$ oxidation state. They acquire half filled $\left(4f^7\right)$ and completely filled $\left(4f^{14}\right)$ electronic configurations.