Question

In which of the following element, both ultimate and penultimate shells are incompletely filled?

• A. Ni
• B. Cd
• C. Hg
• D. Zn

Answer 1

The correct option is A Ni

The electronic configuration of $Ni$ is $1s^2,2s^2{p}^6,3s^2{p}^6{d}^8,4s^2$
Hence, in $Ni$, the ultimate and the penultimate shells are incompletely filled.
The electronic configurations of zinc, cadmium and mercury (penultimate and ultimate shells) are $(n-1)s^2{p}^6{d}^{10},n{s}^2$. Thus, only ultimate shell is incompletely filled whereas penultimate shell is completely filled.