Final answer:
In the order of filling electron sublevels, the 4d sublevel is filled last after 3d, 4s, and 4p sublevels. The correct answer is D) 4d, as it is higher in energy than the other options listed.
Step-by-step explanation:
The order in which electron sublevels are filled is based on their energy levels, which are dictated by the principal quantum number and the angular momentum quantum number. As we fill the electron sublevels, we follow the aufbau principle, which states that electrons occupy the lowest energy sublevel available.
According to the question, we are to identify which sublevel is filled last between 3d, 4s, 4p, 4d, and 5s. Based on electron configuration principles, we fill the 4s sublevel before the 3d because it is lower in energy. After the 4s and 3d, we fill the 4p, followed by the 5s, and finally, we fill the 4d sublevel. Therefore, the correct answer is D) 4d. The periodic table structure reflects this order, where elements in the s-block are filled first, followed by the d-block, and subsequently the p-block.