Electron Configuration Tool

Generate an electron configuration by submitting an atomic number, element symbol, or chemical name.

Instructions

What is computed?

This tool has evolved over time. As of February 27 of 2016, the tool uses an algorithm based on the tutorial A Novel Mnemonic for the Rydberg Rule (Garcia, 2016). That is, the electron configurations of elements in groups 1 and 2 are written according to the Madelung Rule, where the filling order of atomic orbitals is given by the energy levels sequence
ε_nl = (n - 1)p << ns < (n - 2)f < (n - 1)d < np (1)

By contrast, the electron configurations of elements in groups 3 to 18 are written according to the Rydberg Rule. This rule states that the filling order of atomic orbitals is given by

ε_nl = (n - 1)p << (n - 2)f < (n - 1)d < ns < np (2)

In sequences (1) and (2), n = 1, 2, 3, ... is the principal quantum number and l = 0, 1, 2, 3 ... the azimuthal quantum number, corresponding to the s, p, d, and f atomic orbitals (Goudsmit & Richards, 1964). In both sequences, < represents an energy gap and << a large energy gap (Schwarz, 2013, 2010a, 2010b; Schwarz and Rich, 2010; Wang, Qiu, Fang, and Schwarz, 2006; Wang and Schwarz, 2009). Figure 1 shows the mnemonics that summarize these rules and sequences.

(a) Madelung Mnemonic

(b) Rydberg Mnemonic

Figure 1. Mnemonics summarizing the Madelung (a) and Rydberg (b) rules. The arrows in (a) correspond to a constant (n + l) value while in (b) this value is maximized. The large energy gaps (<<) are depicted in the arrows as resembling a backbone. These energy gaps have been found responsible for the periodicity of elements (Wang & Schwarz, 2009; Restrepo & Pachón, 2007).

As explained in the tutorial, sequence (2) can be derived from sequence (1) by reordering the ns orbitals, like this

Madelung and Rydberg Rules

Figure 2. Qualitative derivation of the Rydberg Rule from the Madelung Rule. A complete explanation of this diagram is available (Garcia, 2016).

Said reordering can be used to justify the following algorithm, which is the one used by our tool.
- Because our tool processes Z values ranging from 1 to 120, we use the electron configuration of unbinilium, ₁₂₀Ubn, as a reference configuration. So we assume that for a free neutral atom of Ubn in vacuum, its configuration is given by sequence (1).
- The reference configuration is stored as a $k => $v associative array where $k = nl orbitals and $v = number of electrons in $k. All electron configurations are obtained by parsing and deconstructing the reference configuration.
- Next, a Z value is obtained from the query and compared against a loop that processes configurations derived from the reference configuration. If Z belongs to an element from groups 3 to 18, we simply reorder its configuration according to sequence (2). The entire process is transparent to the end user.
Finally, computed and experimentally determined electron configurations are compared and both results returned. For this purpose, we use the results excellently documented by Scerri (2012a, 2012b, 2013), Schwarz (2013, 2010a, 2010b), Schwarz and Rich (2010), Wang, Qiu, Fang, and Schwarz (2006), and Wang and Schwarz (2009).
As the tool uses the most recent results (Gunther, 2015; Kramida et al., 2014; Saito, 2000; Sato et al., 2015; Siegfried, 2015; Vanquickenborne, et al., 1994; Wikipedia, 2016a, 2016b, 2016c), some results might differ from outdated chemistry resources and sites, particularly from those that incorrectly apply the Madelung Rule and its many flaws across the periodic system of elements.

Who can use this tool?

Suggested Exercises

Acknowledgements

References

Feedback

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