How many electrons in an atom may have `n=4 and m_(s)=+(1)/(2)` ?

Explanation

For `n=4tol` values are 0,1,2,3
`l=0tos` contains 1 electron with `m_(s)=+1/2`
`l=1top` contains 3 electron with `m_(s)=+1//2`
`l=2tod` contains 5 electron with `m_(s)=+1//2`
`l=3tof` contains 7 electron with `m_(s)=+1//2`
`:.` Total no. of electrons with `m_(s)=+1//2` for n=4
`=1+3+5+7=16`