# What is the electron configuration of tungsten?

##### 1 Answer
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.

$\left[X e\right] 5 {d}^{4} 6 {s}^{2}$

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

The $6 s$ orbital of tungsten being slightly above the $5 d$ orbitals (by about $\text{0.24 eV}$) makes it so that it is OK for the $6 s$ 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 $5 d$ and $6 s$ orbitals being large enough to hold electron density fairly well, which stabilizes the paired electron enough.