Question

what is aufbau principal

Answer 1

The aufbau principle states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s shell is filled before the 2s subshell is occupied. ... Aufbau is a German noun that means construction or "building-up".

Answer 2

Aufbau principal states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before filling in higher levels.