What is the electron configuration of tungsten?

1 Answer
Truong-Son N.
Oct 23, 2017

Tungsten has a regular electronic configuration. Being in period 6 and column 6, we expect it to have a d^4 configuration and it sure does.

[Xe] 5d^4 6s^2

But unlike what you may think, this IS an exception to the Aufbau Principle. Consider the data from Appendix B.9:

Data from Appendix B.9 of Inorganic Chemistry by Miessler, Fischer, and Tarr

The 6s orbital of tungsten being slightly above the 5d orbitals (by about "0.24 eV") makes it so that it is OK for the 6s electrons to be paired without too much of a loss of stability, even though it goes against the Aufbau Principle to favor pairing an electron in the highest-energy orbital.

The fact that tungsten has this configuration follows from the 5d and 6s orbitals being large enough to hold electron density fairly well, which stabilizes the paired electron enough.

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