Answer:
n = 3
Step-by-step explanation:
A d subshell has a secondary quantum number, l = 2.
The allowed values for l are 0, 1, 2, 3, … n – 1.
We can write this mathematically as
l ≤ n – 1 Add 1 to each side
l +1 ≤ n Reverse the inequality
n ≥ l + 1
Thus, if l = 2, n ≥ 3
Thus, the lowest energy level where you can find a d subshell is n = 3.