Question

A possible set of quantum numbers for the last electron added to complete an atom of potassium in its ground state is

a) n=4, l=0, ml=0, ms= -1/2
b) n=3, l=1, ml=0, ms= -1/2
c) n=4, l=1, ml=0, ms= +1/2
d) n=3, l=1, ml=1, ms= +1/2
e) n=4, l=2, ml=1, ms= +1/2

I want to say the answer is A because I got the quantum numbers

n =4, l=0, ml=0, ms =+1/2

However, answer choice A has the -1/2 for the magnetic spin. Is +1/2 correct for potassium?

Answer 1

Answer A. The sign for the electron spin is arbitrary, as the spin axis is arbitrary, if based on anything, it is an external magnetic field. There is no difference in energy levels, or order of filling the +- 1/2 spins.

Answer 2

Pls can u explain part of the answer seperate