Question

What is meant by aufbau principle

Answer 1

In the ground state of atoms,the orbitals are filled in order of their increasing energies i.e.,according to (n+l) rule.

Answer 2

Aufbau Principle states that electrons must fill a lower sublevel before starting to fill a higher sublevel. Hopefully, you already know that each sublevel has a specific number of orbitals, and each orbital needs two electrons to be filled. For example, the sublevel 2p has three orbitals, and needs a total of 6 electrons to fill it. Before the 2p orbital is filled, you can not move on to fill 3s, 3p, or 3d orbitals, because they are on a higher sublevel.