Question

Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.

	Electronic configuration		Electron gain enthalphy/KJ ${\text{mol}}^{-1}$
A	$1s^{2}2s^{2}2p^6$	(i)	-53
B	$1s^{2}2s^{2}2p^{6}3s^1$	(ii)	-328
C	$1s^{2}2s^{2}2p^5$	(iii)	-141
D	$1s^{2}2s^{2}2p^4$	(iv)	+48

Answer 1

Analyzing and understanding all the options given:

The electron gain enthalpy refers to the amount of energy that gets released upon the acceptance of an electron from any neutral isolated gaseous atom to form a negative gaseous ion (anion) in the process.

$1s^{2}2s^{2}2p^6$

This configuration correspond to noble gas (i.e. neon) and we know noble gases have positive value of electron gain enthalpy. So, it is perfectly matched with $+48kJ/mol\left(\text{option iv}\right)$ .

As in noble gases outermost shell is fully filled, So, it have large positive electron gain enthalpies because the electron has to enter the next higher principal quantum level leading to a very unstable electronic configuration

$1s^{2}2s^{2}2p^{6}3s^1$

This electronic configuration correspond to alkali metal (i.e. sodium). As we know alkali metals have small negative electron gain enthalpy values because metals have natural tendency to lose electron. So, it is perfectly matched with $-53kJ/mol\left(\text{option i}\right).$

$1s^{2}2s^{2}2p^5$

This electronic configuration correspond to halogens (i.e. fluorine). As we know fluorine have 2nd highest negative electron gain enthalpy in the periodic table (chlorine have highest).

hence the correct matching is…

	Electronic configuration		Electron gain enthalphy/KJ ${\text{mol}}^{-1}$
A	$1s^{2}2s^{2}2p^6$	(iv)	+48
B	$1s^{2}2s^{2}2p^{6}3s^1$	(i)	-53
C	$1s^{2}2s^{2}2p^5$	(ii)	-328
D	$1s^{2}2s^{2}2p^4$	(iii)	-141