Identify the element having highest value of first ionization enthalpy.

If four different elements $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and D having outer electronic configuration as,

$$ \mathrm{A}=3 \mathrm{~s}^2 3 \mathrm{p}^4, \mathrm{~B}=3 \mathrm{~s}^2 3 \mathrm{p}^5, \mathrm{C}=4 \mathrm{~s}^2 4 \mathrm{p}^4, \mathrm{D}=4 \mathrm{~s}^2 4 \mathrm{p}^5 $$

identify the element with lowest ionization enthalpy $\left(\Delta_1 \mathrm{H}_1\right)$

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

Find the element having highest ionization enthalpy $\left(\Delta_1 \mathrm{H}_1\right)$