Which of the following quantum number combinations is not allowed in an atom? a. n = 2, l = 1, m subscript l = 0 b. n = 1, l = 0, m subscript l = 0 c. n = 4, l = 3, m subscript l = -3 d. n = 2, l = 3, m subscript l = 2

TLDR: It’s D.

This is a principle of quantum chemistry, where a subset of n, l, m, and s numbers identify a specific type of atom. The Pauli Exclusion Principle states that two elements that are not the same can not have the same four quantum numbers.

N represents the principal quantum number, L represents the azimuthal quantum number, M represents the magnetic quantum number, and S represents the atomic spin.

The rules are as follows:
L < N
M= -L to + L
S = +,- 1/2 (although this one doesn’t matter since it isn’t asked)

Therefore, D doesn’t work as the azimuthal quantum value exists outside of the principal boundary that L must be less than N (3 /< 2).