Question

elements of the fourth period fill the 4s sublevel with electrons before filling the 3d sublevel. Also, some elements move an electron from a filled 4s sublevel to an unoccupied 3d sublevel. Explain these behaviors

Answer 1

Answer:

Elements fill the lowest energy subshells first(Aufbau's rule), and the 4s subshell is lower energy than the 3d, making the labeling deceiving. In some rare situations, the electrons would rather have Hund's rule be respected more, having all electrons facing one way with no doubled up because it is more stable(these are pretty rare and usually deal with transition metals like copper).

Hope this helps!

Explanation: