Final answer:
For n = 4 and ml = -2, there is only one orbital, which is one of the five d orbitals in the d subshell of the n = 4 shell.
Step-by-step explanation:
The question asks about the number of orbitals an atom can have with quantum numbers n = 4 and ml = -2. For n = 4, there can be subshells with angular momentum quantum number values (l) of 0, 1, 2, and 3, corresponding to s, p, d, and f subshells respectively. The magnetic quantum number (ml) describes the orientation of the orbital in space relative to the other orbitals in that subshell.
For l = 2 (the d subshells), ml can have values of -2, -1, 0, +1, and +2, corresponding to the five d orbitals. Since the question specifies ml = -2, we look at the d subshells and find exactly one orbital that corresponds to this magnetic quantum number. Therefore, there is only one orbital in an atom with n = 4 and ml = -2.