Q. The maximum number of electrons that can have principle quantum number, $n = 3$ and spin quantum number, $m_{s} = - \frac{1}{2}$, is
A) 3
B) 5
C) 7
D) 9
Explanation
(d)
When $n = 3,l = 0,\ 1,\ 2\ i.e.,\$there are 3$s$, 3$p$ and 3$d$-orbital’s. If all these orbitals are completely occupied as
[image:2_image27.emf]
Total 18 electrons, 9 electrons with $s = + \frac{1}{2}$ and 9 with
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ s = - \frac{1}{2}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.