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The '''Aufbau principle''', also known as the ''building-up rule'', is a method for determining the configuration of [[electron|electrons]] in an [[atom]] or [[ion]]. The rule states that the electrons surrounding a nucleus can be "built up" by first occupying the most stable orbitals, often those of the lowest energy level.
The '''Aufbau principle''', also known as the ''building-up rule'', is a method for determining the configuration of [[electron|electrons]] in an [[atom]] or [[ion]]. The rule states that the electrons surrounding a nucleus can be "built up" by first occupying the most stable [[orbital]]s, often those of the lowest energy level.
===Example===
===Example===
This principle can be illustrated by examining the distribution of electrons in an atom of [[carbon]]. The six electrons surrounding a stable carbon [[nucleus]] would be built up the following way - first, an electron would be added to the 1s orbital. This is the lowest energy orbital and closest to the nucleus. By applying the [[Hund rule]] in conjunction with the Aufbau principle, one can determine that the second electron will also occupy the 1s orbital. The [[Pauli Exclusion principle]] then yields that any further electrons must be added to the 2s shell. After both the 1s and 2s orbitals are full (for a total of four electrons), electrons may be added to the next highest energy level, the 2p orbital; the two remaining electrons can be found here. This process yields the electron configuration of carbon as ''1s<sup>2</sup> 2s<sup>2</sup> 2p<sup>2</sup>''.
This principle can be illustrated by examining the distribution of electrons in an atom of [[carbon]]. The six electrons surrounding a stable carbon [[nucleus]] would be built up the following way - first, an electron would be added to the 1s orbital. This is the lowest energy orbital and closest to the nucleus. By applying the [[Hund rule]] in conjunction with the Aufbau principle, one can determine that the second molecule will also occupy the 1s orbital. The [[Pauli Exclusion principle]] then yields that any further electrons must be added to the 2s shell. After both the 1s and 2s orbitals are full (for a total of four electrons), electrons may be added to the next highest energy level, the 2p orbital; the two remaining electrons can be found here. This process yields the electron configuration of carbon as ''1s<sup>2</sup> 2s<sup>2</sup> 2p<sup>2</sup>''.
[[Category:Chemistry]]
[[Category:Chemistry]]