Final answer:
l cannot equal 4 when n is 3 because the angular momentum quantum number l must be an integer that is at least 0 and less than the principal quantum number n, thus l can range from 0 to n-1.
Step-by-step explanation:
The value of l, also known as the angular momentum quantum number or azimuthal quantum number, has specific limitations in relation to the principal quantum number n. By definition, for a given value of n, the value of l can take on any integer value from 0 up to (but not including) n. So for n = 3, the values of l can be 0, 1, or 2. l cannot equal 4 because it must always be less than n.
Answering your question directly, l can never equal 4 when n is equal to 3 because it would violate the rule that l < n. Essentially, this limitation ensures that the right amount of subshells and corresponding orbitals are available within each principal energy level, adhering to the principles of quantum mechanics.