Final answer:
The most stable electron configuration of the 4f energy sublevel is 4f14.
Step-by-step explanation:
The most stable electron configuration of the 4f energy sublevel is 4f14. This is because each orbital in the 4f sublevel can accommodate 2 electrons and there are a total of 7 orbitals in the 4f sublevel. Therefore, 7 x 2 = 14 electrons can be accommodated in the 4f sublevel, making 4f14 the most stable configuration.