Question
The correct order of ionic radii of $$Ce,La,Pm$$ and $$Yb$$ in +3 oxidation state is
A.
$$L{a^{3 + }} < P{m^{3 + }} < C{e^{3 + }} < Y{b^{3 + }}$$
B.
$$Y{b^{3 + }} < P{m^{3 + }} < C{e^{3 + }} < L{a^{3 + }}$$
C.
$$L{a^{3 + }} < C{e^{3 + }} < P{m^{3 + }} < Y{b^{3 + }}$$
D.
$$Y{b^{3 + }} < C{e^{3 + }} < P{m^{3 + }} < L{a^{3 + }}$$
Answer :
$$Y{b^{3 + }} < P{m^{3 + }} < C{e^{3 + }} < L{a^{3 + }}$$
Solution :
The overall decrease in atomic and ionic radii from $$L{a^{3 + }}$$ to $$L{u^{3 + }}$$ is called lanthanoid contraction. Hence, the correct order is $$Y{b^{3 + }} < P{m^{3 + }} < C{e^{3 + }} < L{a^{3 + }}$$