Which type of subshell is filled after 4s in the order of electron configuration?

The order in which subshells are filled in electron configurations follows the Aufbau principle, which states that electrons occupy the lowest energy orbitals first.

After the 4s subshell is filled, the next subshell to be filled is the 3d subshell. Although the 3d subshell begins at the same principal quantum number (n=3) as the 4s subshell, d orbitals have a higher energy than s orbitals when considering their placement in the periodic table. However, in the actual filling sequence, the 4s subshell is filled first due to its lower energy in the context of the ground state electron configuration for elements.

After all available 4s electrons are placed, the next available orbitals include the 3d subshell. This is based on the energy level and the stability of the electron configuration.

It is important to note that the 5s subshell, located at a higher principal quantum level than 4s, cannot be filled before 3d due to the gap in energy, thus it does not come after the 4s subshell in terms of filling order. Similarly, the 4p and 4d subshells also come later in the