Aufbauperiaate

Aufbauperiaate is not a standard term in chemistry; the correct and widely used designation is Aufbauprinzip, or the Aufbau principle. It describes how electrons fill atomic orbitals to form the ground-state electron configuration of atoms. The name derives from the German word for “to build up.”

According to the Aufbau principle, electrons occupy the lowest-energy orbitals available, and they do so in a way that obeys the Pauli exclusion principle and Hund’s rule. The approximate order in which subshells are filled is captured by the Madelung rule, which orders orbitals by increasing n + l and, for equal values, by smaller n. A common sequence used to build up electron configurations is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.

Limitations and deviations exist. In multi-electron atoms, electron–electron interactions shift orbital energies, so the simple order can be altered, particularly for transition metals and lanthanides. Classic anomalies include chromium and copper, where the actual ground-state configurations involve partial or full occupation patterns that differ from the naive order due to exchange energy and stability considerations.

Applications of the Aufbau principle lie in predicting and understanding ground-state electron configurations, which influence chemical properties and periodic trends. It serves as a practical, if approximate, model in teaching and basic chemistry, while exact results require full quantum-mechanical calculations for many-electron systems.