For up to period 3, elements' electron configurations are relatively easy to work out until the transition metals begin. Then some elements may have $\ce{4s}$ orbitals which are preferred by electrons over $\ce{3d}$ orbitals. These small rules don't make sense all the time and only cover some elements. Is their any master method for working out the electron configurations of any given element?

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    $\begingroup$ No, at least not by hand. The Aufbau Principle is only a guideline but in later elements many different effects are at play which are nearly impossible to consider without doing a thorough calculation. Maybe this question is of interest to you. $\endgroup$
    – Philipp
    Sep 25, 2014 at 17:16

1 Answer 1


There is a semi-empirical method to fill the atomic orbitals: atomic orbitals are filled in the order of increasing n+l. If the sum n+l is equal for two atomic orbitals, they are filled in order of increasing n. This gives the following order for filling the orbitals: 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


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