Question

Which among the following contain partially filled $d$ subshell and does not show variable oxidation states?

• A. $Cd$
• B. $Hg$
• C. $Zn$
• D. $La$

Answer 1

Answer: (D)

$La$

$La$ contains partially filled $d$ subshell and does not show variable oxidation states.

The electronic configuration of $La$ is $\left[Xe\right]4f^{0}5d^{1}6s^2$

$La$ shows only +3 oxidation state by losing two $6s$ electrons and the one $5d$ electron. The $L{a}^{3+}$ ion so formed has the configuration of xenon which is highly stable.

$Zn,Cd$ and $Hg$ have completely filled $(n-1)d$ orbitals.

Hence the correct option is D.