Question

Electronic configurations of four elements $A,B,C$ and $D$ are given below:
(A) $1s^{2}2s^{2}2p^6$
(B) $1s^{2}2s^{2}2p^4$
(C) $1s^{2}2s^{2}2p^{6}3s^1$
(D) $1s^{2}2s^{2}2p^5$
Which of the following is the correct order of increasing tendency to gain electron?

• A. $A<C<B<D$
• B. $A<B<C<D$
• C. $B<A<C<D$
• D. $D<A<B<C$

Answer 1

The correct option is A $A<C<B<D$

(A) $1s^{2}2s^{2}2p^6$: Total electrons $=2+2+6=10$ Its a completely filled electronic cofiguration i.e. group 18 element Neon. This element has positive electron gain enthalpy.

(B) $1s^{2}2s^{2}2p^4$: The electronic configuration is for group 16 element i.e. oxygen. This elementhas high negative electron gain enthalpy.

(C) $1s^{2}2s^{2}2p^{6}3s^1$: The electronic configuration is for group 1 element i.e. Sodium. This element has low negative electron gain enthalpy.

(D) $1s^{2}2s^{2}2p^5$: The electronic configuration is for group 17 element i.e. Fluorine. This element has highest negative electron gain enthalpy among the given configurations.

Thus increasing order of elelctron gain enthalpies for the given configurations is:

$A<C<B<D$