Is this a possible quantum number:

Question

3,2,2,-1/2

This is my thikning:
n=3
so therefore l = 0-2
so therefore ml could = 2

However, many of my classmates said it was impossible.

Answer 1

I agree with you. Have your classmates go through it like this.
n = 3
thus, l = 0, 1, or 2.
For l = 0, ml may be 0
For l = 1, ml may be -1, 0, or +1
For l = 2, ml can be -2, -1, 0. +1, or +2.
Then m_s may be +/- 1/2

Answer 2

Thank you :)