Question

Why the last electron of K element goes to 4s orbital instead of 3d ? Explain

Answer 1

Answer:

We know that the 4s electrons are lost first during ionization. The electrons lost first will come from the highest energy level, furthest from the influence of the nucleus. So the 4s orbital must have a higher energy than the 3d orbitals.

Answer 2

Answer:

The last electron in potassium enters the 4s orbital rather than the 3d orbital because the the 4s orbital has a lower energy level than the 3d orbital. The Aufbau principle states that electrons occupy the lowest available energy level in the ground state.