Question

Which 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

$3-{1s}^2{2s}^{1}12-{1s}^2{2s}^2{2p}^6{4s}^2$

In both elements, the valence electron enters s-block. Therefore, it a s-block element.