An element z has an electronic configuration : $n{s}^{2}n{p}^6$$(n-1)d^{10}(n-2)f^{14}$. Which value of n is not possible

For n=6,

$6s^2,6p^6,5d^{10},4f^{\mathrm{\prime }4}$

This is a possible electronic configuration.

For n=3,

$\begin{array}{l}\mathit{\Rightarrow }\mathit{3}{\mathit{s}}^{\mathit{2}}\mathit{,}\mathit{3}{\mathit{p}}^{\mathit{6}}\mathit{,}\mathit{(}\mathit{3}\mathit{-}\mathit{1}\mathit{)}{\mathit{d}}^{\mathit{10}}\mathit{(}\mathit{3}\mathit{-}\mathit{2}\mathit{)}{\mathit{f}}^{\mathit{14}}\\ \mathit{\Rightarrow }\mathit{3}{\mathit{s}}^{\mathit{2}}\mathit{,}\mathit{3}{\mathit{p}}^{\mathit{6}}\mathit{,}\mathit{2}{\mathit{d}}^{\mathit{10}}\mathit{,}\mathit{1}{\mathit{f}}^{\mathit{14}}\end{array}$

This is not possible.

For n=5,

$5s^{\mathit{2}},s{p}^{\mathit{6}}4d^{\mathit{10}}3f^{\mathit{14}}$

This is not possible.