# Identify the elements X and Y using the ionisation energy values given below:

Question:

Identify the elements $X$ and $Y$ using the ionisation energy values given below:

1. $\mathrm{X}=\mathrm{Na} ; \mathrm{Y}=\mathrm{Mg}$

2. $\mathrm{X}=\mathrm{Mg} ; \mathrm{Y}=\mathrm{F}$

3. $\mathrm{X}=\mathrm{Mg} ; \mathrm{Y}=\mathrm{Na}$

4. $\mathrm{Y}=\mathrm{F} ; \mathrm{Y}=\mathrm{Mg}$

Correct Option: 1

Solution:

$\mathrm{Na} \rightarrow[\mathrm{Ne}] 3 \mathrm{~s}^{1} \mathrm{IE}_{1}$ is very low but $\mathrm{IE}_{2}$ is very

high due to stable noble gas configuration of $\mathrm{Na}^{+}$

$\mathrm{Mg} \rightarrow[\mathrm{Ne}] 3 \mathrm{~s}^{2} \mathrm{IE}_{1} \& \mathrm{IE}_{2} \rightarrow$ Low

$E_{3}$ is very high.