Q. Which of the atomic number pairs represents elements of $s$-block?
A) 7, 15
B) 5, 12
C) 9, 17
D) 3, 12
Explanation
(d)
In $s$-block elements, electron enter into the $ns$-orbitals.
For atomic number 3=$1s^{2},2s^{1}$
Atomic number 12=$1s^{2},2s^{2}2p^{6},3s^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.