Question

Which of the following pair of atomic numbers represents s-block elements?

• A. $7,15$
• B. $6,12$
• C. $9,17$
• D. $3,12$

Answer 1

The correct option is D $3,12$

The general outer electronic configuration of $s$ block elements are $n{s}^{1-2}$.
Consider the options available:-
A) $7-\left[He\right]2s^{2}2p^3,15-\left[Ne\right]3s^{2}3p^3$.
B) $6-\left[He\right]2s^{2}2p^2,12-\left[Ne\right]3s^2$.
C) $9-\left[He\right]2s^{2}2p^5,17-\left[Ne\right]3s^{2}3p^5$.
D) $3-\left[He\right]2s^1,12-\left[Ne\right]3s^2$.
Hence, from the options we see that D is the right answer.