I was reading on Wikipedia about how Pauling electronegativities are determined through

$$ \vert \chi_\ce{A} - \chi_\ce{B} \vert = \sqrt{E_\mathrm{d}(\ce{AB}) - \frac{E_\mathrm{d}(\ce{AA}) + E_\mathrm{d}(\ce{BB})}{2}}$$

At first, I thought I understood this since for an element like hydrogen the meaning of $E_\mathrm{d}(\ce{HH})$ is clear and easy enough to measure experimentally.

But I don't see how I would do the measurement in general. Do I have to make (unstable) diatoms and then try to measure the dissociation energy very quickly? Even the electronegativity for atoms with $Z > 100$ are known which baffles me. How do they measure these dissociation energies?

  • 1
    $\begingroup$ Off the top of my head, I believe the answer is that the element simply needs to bond covalently or metallically with itself when it is in its standard state. Its standard state doesn't need to be a diatomic. The metals form metallic bonds. The metalloids and non-metals (except the noble gases) form covalent bonds. For instance, carbon's standard state is graphite. The BDE for the C-C bond would then be the average energy it takes to break apart the C-C bonds in graphite. Other than the noble gases, I don't know of any elements that don't chemically bond with themselves. $\endgroup$
    – theorist
    Dec 1, 2021 at 5:35


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