Madelungs Rule Definition and Example

Madelungs Rule Definition and Example Madelungs Rule Definition Madelungs 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 Madelungs rule or Klechkowskis rule originally was described by Charles Janet in 1929 and rediscovered by Erwin Madelung in 1936. V.M. Klechkowski described the theoretical explanation of Madelungs rule. The modern Aufbau principle is based on Madelungs rule. Also Known As: Klechkowskis rule, Klechowsy rule, diagonal rule, Janet rule Exceptions to Madelungs Rule Keep in mind, Madelungs rule may only be applied to neutral atoms in the ground state. Even then, there are exceptions from the ordering predicted by the rule and experimental data. For examples, the observed electron configurations of copper, chromium, and palladium are different from predictions. The rule predicts the configuration of  9Cu to be 1s22s22p63s2  3p64s23d9  or [Ar]4s23d9  while the experimental configuration of a copper atom is [Ar]4s13d10. Filling the 3d orbital completely gives the copper atom a more stable configuration or lower energy state.