Which of the following sets of quantum numbers is not allowed? A.) n=3, l=2, ml=-2
B.) n=4, l=3, ml=-3
C.) n=2, l=1, ml=-1
D.) n=2.5, l=0, ml=0
E.) n=3, l=2, ml=-1

D) n = 2.5, ℓ = 0, mℓ = 0

Explanation:

According to the rules governing acceptable quantum numbers, the value for n must be an integer. Therefore, the set {n = 2.5, ℓ = 0, mℓ = 0} is not allowed.