From the list given below, the number of lanthanides which exhibit +4 state in their oxides is Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy

Step-by-step solution

Pr , Nd , Tb and Dy exhibit +4 state in their oxides as they acquire configurations closer to stable 4 f ^ and 4 f ^7 configurations. aligned & Pr ⁴⁺=[ Xe ] 4 f ^1, Nd ⁴⁺=[ Xe ] 4 f ^2, Pm ⁴⁺=[ Xe ] 4 f ^3 & Sm ⁴⁺=[ Xe ] 4 f ^4, Eu ⁴⁺=[ Xe ] 4 f ^5, Gd ⁴⁺=[ Xe ] 4 f ^6, & ~Tb ⁴⁺=[ Xe ] 4 f ^7, Dy ⁴⁺=[ Xe ] 4 f ^6 . aligned