Which subshells are filled in order after 4p?

The correct answer involves understanding the order of subshell filling as dictated by the Aufbau principle, which states that electrons occupy the lowest energy orbitals available before moving to higher energy subshells.

After the completion of the 4p subshell, the next subshell to be filled is the 5s. This is because, despite the 4d subshell being available, the 5s has a lower energy level compared to the 4d subshell. The order of filling generally follows the sequence governed by the n+l rule, where 'n' is the principal quantum number and 'l' is the azimuthal quantum number (0 for s, 1 for p, 2 for d, and 3 for f).

In this case, the 5s subshell has n=5 and l=0, which gives it a total of 5, while the 4d subshell has n=4 and l=2, resulting in a total of 6. Since lower total values signify lower energy levels, the electrons will fill the 5s subshell next, followed by filling the 4d subshell afterward.

Therefore, once the 4p subshell is fully occupied, the