Ncert Exercises & Solutions

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.

Column I (Electron configuration)	Column II (Electron gain enthalpy/kJ mol^-1)
A. $1 s^{2} 2 s^{2} 2 p^{6}$	1. -53
B. $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}$	2. -328
C. $1 s^{2} 2 s^{2} 2 p^{5}$	3. -141
D. $1 s^{2} 2 s^{2} 2 p^{4}$	4. +48

Codes

Options:	A	B	C	D
1.	4	1	2	3
2.	1	2	3	5
3.	1	4	3	2
4.	4	1	3	2

A. $\to$ (4) B. $\to$ (1) C. $\to$ (2) D. $\to$ (3)

A. This electronic configuration corresponds to the noble gas i.e., neon. Since, noble gases have

+ ∆_{eg} H

values, therefore, electronic configuration (A) corresponds to the

∆_{eg} H = + 48 kJ {mol}^{- 1}

B. This electronic configuration corresponds to the alkali metal i.e., potassium. Alkali metals have small negative

∆_{eg} H

values, hence, electronic configuration (B) correspongds to

∆_{eg} H = - 53 kJ {mol}^{- 1}

C. This electronic configuration corresponds to the halogen i.e., fluorine. Since, halogens have high negative

∆_{eg} H

values, therefore, electronic configuration (C) corresponds to

∆_{eg} H = 328 kJ {mol}^{- 1}

D. This electronic configuration corresponds to the chalcogen i.e., oxygen. Since, chalcogens have

∆_{eg} H

values less negative than those of halogens, therefore, electronic configuration (D) corresponds to

∆_{eg} H = - 141 kJ {mol}^{- 1}

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