How many electrons in an atom may have the following quantum numbers?
(a) ` n=4 , m_(s) =-1//2` (b) n=3 , l=0

Explanation

(a) For n = 4 shell, total number of electrons
`= 2n^2= 2 xx (4)^2= 32`
Half of them, i.e., 16 electrons will have
`m_(s)=-1/2`
(b) For n=3 shell
`l=0, m_(l)=0 and m_s=+1/2 and -1/2`
Thus, there will be two electrons with quantum numbers
`3,0, 0, +1//2 and 3,0 ,0, -1//2`