Which sub-shell contains the highest energy electrons in a given principal energy level?

The sub-shell that contains the highest energy electrons in a given principal energy level is the f sub-shell. The reason for this lies in the structure of atomic orbitals and the energy levels associated with them.

As principal energy levels increase (n = 1, 2, 3, etc.), the complexity and energy of the sub-shells also increase. For any given principal energy level, the hierarchy of energy from lowest to highest goes as follows: s sub-shells have the lowest energy, followed by p sub-shells, then d sub-shells, and finally f sub-shells.

This ranking reflects how these sub-shells are filled with electrons according to the Aufbau principle, which dictates that electrons occupy the lowest available energy orbitals first. Therefore, within the same principal energy level, f sub-shells contain electrons that are higher in energy compared to s, p, and d sub-shells.

Thus, since the f sub-shell is the last to be filled and has the highest energy for a given principal energy level, it is correct to say that it contains the highest energy electrons in that context.