1. The problem statement, all variables and given/known data Why is the spin quantum number either +1/2 or -1/2 2. Relevant equations N.A. 3. The attempt at a solution I am not sure but this is the way i thought of it. Whatevrr quantum numbers i have known of so far: Principal, Azumithal tc. all of them have a diffrence of one between any two consecutive quantum numbers. Therefore the magnitude of the quantum numbers are +/- 1/2. Same magnitude because the the electrons are the same in all respects.Negative because the elecrons are spinning in opposite direstions. This explanation has no mathematical backup and is just by observation and just wanted to know wether the observation was good enough.