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. $D<B<C<A$
• 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: $A<C<B<D$.