CHEM101: General Chemistry I

Our third video shows how to use the Aufbau Principle when filling electrons in orbitals for larger elements. This principle tells us that we fill electrons from the lowest energy to the highest energy.

The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones (Aufbau is German for 'building-up'). By following this rule, we can predict the electron configurations for atoms or ions. The Aufbau principle is most useful for the first 20 elements: from Sc on, the Aufbau principle does not accurately predict the order of electron filling in atoms.