Final answer:
The incorrect orbital notation among the choices provided is (c) ₃f, because f orbitals do not exist in the third energy level; they begin at the fourth energy level (n=4).
Step-by-step explanation:
The question pertains to the validity of orbital notation in accordance with quantum number rules. Specifically, you need to determine which of the following is an incorrect orbital notation: (a) ₄dxy, (b) ₄s, (c) ₃f, (d) ₃py ₂s. Considering the quantum numbers, which dictate the possible orbitals within electron shells, we can eliminate (a) ₄dxy and (d) ₃py ₂s from being incorrect as these notations comply with known electron configurations. On the other hand, orbital notation (c) ₃f is incorrect because f orbitals do not exist in the third energy level (n=3); they start from the fourth energy level (n=4). Lastly, (b) ₄s is a valid notation for the s orbital in the fourth energy level. Therefore, the incorrect orbital notation here is (c) ₃f.