What electron could have quantum numbers n = 2, l = 1, ml = 0, ms = + ?

Answer is: electron in 2pz orbital.

The principal quantum number is one of four quantum numbers which are assigned to each electron in an atom to describe that electron's state, n=1,2,3 ... n=2 - the second energy level.

The azimuthal quantum number is a quantum number for an atomic orbital that determines its orbital angular momentum and describes the shape of the orbital. l = 0,1 ... n-1, when l = 1, that is p subshell.

The magnetic quantum number, ml, show orbital in which the electron is located, ml = - l ... + l, ml = 0 is pz orbital.

The spin quantum number, ms, is the spin of the electron; ms = + 1/2 or - 1/2.