Final answer:
The correct electron configuration should fill the 4s sublevel before the 3d sublevel. As none of the given options include 4s², the correct configuration starting after 3p⁶ should be 1s² 2s² 2p⁶ 3s² 3p⁶ 4s², followed by 3d.
Step-by-step explanation:
The correct electron configuration for an atom after filling the 3s and 3p sublevels would proceed to fill the 4s sublevel before filling the 3d sublevel. This is due to the 4s sublevel having a lower energy than the 3d sublevel. Therefore, the configuration listed as "1s² 2s² 2p⁶ 3s² 3p⁶ 3d?" must be incorrect since the 4s should be filled before 3d.
The correct configurations based on the given choices are:
- a. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²
- b. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰
- c. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸
- d. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶
Keeping in mind the energy levels and the Aufbau principle, the correct configuration would be once the 3p sublevel is filled, we add the next two electrons to the 4s sublevel. Therefore, the correct configuration is not given in the options provided, but should be 1s² 2s² 2p⁶ 3s² 3p⁶ 4s², followed by filling the 3d sublevel.