Q. Which pair of the atomic numbers represents $s$-block elements?
A) 3, 12
B) 6, 12
C) 7, 15
D) 9, 17
Explanation
(a)
$3 = 1s^{2},\ 2s^{1}$
$12 = 1s^{2},\ 2s^{2},\ 2p^{6},\ 3s^{2}$
Since, last electron enters in $s$-orbitals, these are $s$-bloc elements
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.