(a) How many sub-shells are associated with n = 4? (b) How many electrons will be present in the sub-shells having `m_(s)`value of `–1//2 for n = 4`?

Explanation

(a) When n=4, l=0, 1,2,3. Thus, there will be four subshells viz, s,p,d and f
(b) For n=4 shell, the total number of orbitals present `=n^2=(4)^2=16`
Each orbitals has one electron wth `m_(s)=-1/2`
Hence there will be 16 electrons with `m_(s)=-1/2`