Building Up Principle

[Kimberly Bauer 4E]

Can someone explain this principle and provide examples?

[Haley Pham 4I]

The building up (Aufbau Principle) states that an electron occupies orbitals in order from lowest to highest energy. The lowest energy sublevel is the 1s sublevel, then as we go on to atoms with multiple electrons, the electrons are added on creating the 2s, 2p, 3s, etc. sublevels.

[Sofia Barker 2C]

The Aufbau Principle is based on the Pauli Exclusion Principle and states that electrons occupy orbitals in a way that creates the lowest energy configuration, or the experimentally observed ground state. This means that electrons in an atom will occupy orbitals that maintain the lowest energy level and build up to higher energy levels. Electrons will occupy the 4s orbital before the 3d orbital because filling the 4s maintains a lower energy configuration and filling the 3d first.