The Aufbau principle (from the German Aufbauprinzip, meaning building‑up principle ) is a rule in atomic physics and quantum chemistry that describes how electrons occupy atomic orbitals in ground‑state atoms or ions. It states that electrons fill available subshells in order of increasing energy, so that the lowest‑energy orbitals are occupied first and higher‑energy orbitals later. Applying this principle , in combination with the Pauli exclusion principle and Hund’s rule, allows ... The Aufbau principle is a crucial chemistry principle for determining an atom’s electron configuration in its ground state. The Aufbau principle requires the atom to adhere to Pauli’s exclusion principle and Hund’s rule, which states that each orbital can initially only hold one electron before becoming doubly occupied (no two electrons in one orbital have same spin). 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 .
