An electron in an atom has the following set of quantum numbers: n = 4, l = 3, ml = +1, ms = + ½. An impossible quantum number set for a second electron in this atom is .....

n = 4, l = 2, ml = - 3, m s = + ½.

n = 3, l = 1, ml = - 1, m s = - ½.

n = 4, l = 1, ml = 0, m s = + ½.

or

n = 2, l = 0, ml = 0, ms = - ½.

If you could explain, i would appreciate it!