Question

Why are $\mathrm{Zn},\mathrm{Cd}\&\mathrm{Hg}$ not transition elements?

Answer 1

Transition elements:

1. According to IUPAC elements having a $d$ subshell that is partially filled with electrons are transition elements.
2. They have the ability to form stable cations with an incompletely filled $d$ orbital.

Here, the orbitals of zinc, cadmium and mercury are completely filled when they are in their ground state also, in their general oxidation state.

The electronic configuration of:

1. Zinc is $\left[Ar\right]3d^{10}4s^2$
2. Cadmium is $\left[Kr\right]4d^{10}5s^2$
3. Mercury is $\left[Xe\right]5d^{10}6s^2$

Hence, $\mathrm{Zn},\mathrm{Cd}\&\mathrm{Hg}$ are not transition elements.