Periodic Table and Periodicity

If $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ are four different elements with outer electronic configuration as $\mathrm{A}=4 \mathrm{~s}^2 4 \mathrm{p}^4, \mathrm{~B}=4 \mathrm{~s}^2 4 \mathrm{p}^5, \mathrm{C}=5 \mathrm{~s}^2 5 \mat...

If four different elements $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and D having outer electronic configuration as,
$$ \mathrm{A}=3 \mathrm{~s}^2 3 \mathrm{p}^4, \mathrm{~B}=3 \mathrm{~s}^2 3 \mathrm{p}^5, \mathrm{C}=4 \mathrm{~s}^2 4 \mathrm{p...

Identify the element having highest value of first ionization enthalpy.