The successive ionisation enthalpies of an element $X$ in $\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ are…
The successive ionisation enthalpies of an element $X$ in $\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ are 1012, 1907, $2955,4955,6275$ and 21,260 respectively, the element $X$ is
C
$\mathrm{P}$
$\mathrm{S}$
$\mathrm{Cl}$
Solution
\begin{array}{ll}
\hline First ionisation enthalpy & 1012 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline Second ionisation enthalpy & 1907 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline Third ionisation enthalpy & 2955 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline Fourth ionisation enthalpy & 4955 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline Fifth ionisation enthalpy & 6275 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline Sixth ionisation enthalpy & 21,260 \mathrm{~kJ} \mathrm{~mol}^{-1} \\
\hline
\end{array}
Since, sixth ionisation enthalpy is much higher, it means that the removal of sixth electron is from the stable configuration, therefore the element is phosphorus $(\mathrm{P})$ having 5 electrons in the valence shell.