Madelung's Rule Definition

Madelung's Rule is used to fill electron orbitals.
Madelung's Rule is used to fill electron orbitals. Todd Helmenstine

Madenlung's Rule Definition

Madelung's rule describes electron configuration and the filling of atomic orbitals. The rule states:

(1) Energy increases with increasing n + l

(2) For identical values of n + l, energy increases with increasing n

The following order for filling orbitals results:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, (8s, 5g, 6f, 7d, 8p, and 9s)

The orbitals listed in parentheses are not occupied in the ground state of the heaviest atom known, Z = 118.

The reason orbitals fill this way is because the inner electrons shield the nuclear charge. Orbital penetration is as follows:
s > p > d >f

Madelung's rule or Klechkowski's rule originally was described by Charles Janet in 1929 and rediscovered by Erwin Madelung in 1936. V.M. Klechkowski described the theoretical explanation of Madelung's rule. The modern Aufbau principle is based on Madelung's rule.

Also Known As: Klechkowski's rule

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Helmenstine, Anne Marie, Ph.D. "Madelung's Rule Definition." ThoughtCo, May. 25, 2016, thoughtco.com/definition-of-madelungs-rule-605325. Helmenstine, Anne Marie, Ph.D. (2016, May 25). Madelung's Rule Definition. Retrieved from https://www.thoughtco.com/definition-of-madelungs-rule-605325 Helmenstine, Anne Marie, Ph.D. "Madelung's Rule Definition." ThoughtCo. https://www.thoughtco.com/definition-of-madelungs-rule-605325 (accessed January 16, 2018).