Aufbau principle: Learn the definition and rules of the

Learn the definition and rules of the Aufbau principle , which states that electrons fill atomic orbitals of the lowest available energy level in the ground state of an atom or ion. See examples of hydrogenic and multi-electron atoms/ions and how to apply Hund's rule and exchange interaction. Learn how electrons are filled in atomic orbitals according to the Aufbau principle , which states that electrons occupy orbitals in increasing order of energy. Find out the exceptions, the (n+l) rule, and how to write electron configurations using the Aufbau principle . Learn how to use the Aufbau principle to construct the electron configuration of atoms in their ground state. The principle states that electrons fill the lowest energy subshells first, according to the sum of their quantum numbers.