Question

Electronic configurations of four elements $A$, $B$, $C$ and $D$ are given below:
(A) $1s^2\, 2s^2\, 2p^6$ $\quad$ (B) $1s^2\, 2s^2\, 2p^4$
(C) $1s^2\, 2s^2\, 2p^6\,3s^1$ $\quad$(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. $D < B < C < A$
• D. $D < A < B < C$

Answer 1

Answer: (A)

$A$ is $Ne(10) : 1s^2 \,2s^2\, 2p^6$
$B$ is $O(8) : 1s^2 \,2s^2\, 2p^4$
$C$ is $Na(11) : 1s^2 \,2s^2\, 2p^6\,3s^1$
$D$ is $F(9) : 1s^2 \,2s^2\, 2p^5$
Noble gases (A) have completely filled orbitals hence, they have no tendency to gain electrons.
Element C prefers to lose electron $(3s^1)$ to attain stable noble gas configuration.
Element D has only 1 electron less than stable noble gas configuration, Thus, It has greater tendency to gain electron than element B which has 2 electrons less than noble gas configuration.
Thus, the correct order of increasing tendency to gain electron Is: $A < C < B < D$.