Question

Why is it impossible for an electron to have the quantum numbers N=three I= 0 M= 1 MS= +1/2

Answer 1

Because, for n=2, l = 0 →n-1. So, l values are 0 and 1. For each l value, there are 2l +1 ml values, -l to +l. As here l = 1, ml should have maximum value +1. So, ml = 3 is not possible, rest three quantum numbers are all right.