what is aufbau's principle?

Aufbau's Principle states that the orbitals are filled in the increasing order of their

energies (in the ground state). Following the (n + l) rule, the orbitals

in the increasing order of energy are arranged as

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f

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Aufbau's Principle states that the orbitals are filled in the increasing order of their

energies (in the ground state). Following the (n + l) rule of Aufbau's principle, the orbitals

in the increasing order of energy are arranged as

1s ƒ¬ 2s ƒ¬ 2p ƒ¬ 3s ƒ¬ 3p ƒ¬ 4s ƒ¬ 3d ƒ¬ 4p ƒ¬ 5s ƒ¬ 4d ƒ¬ 5p

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The Aufbau's Principle  is used to determine the electron configuration of an atom,molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons. As they are added, they assume their most stable conditions with respect to the nucleus and those electrons already there.

According to the principle, electrons fill orbitals starting at the lowest available (possible) energy levels before filling higher levels (e.g. 1s before 2s). The number of electrons that can occupy each orbital is limited by the Pauli exclusion principle. If multiple orbitals of the same energy are available, Hund's rule states that unoccupied orbitals will be filled before occupied orbitals are reused with respect to the nucleus and those electrons already there.

 

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