How exactly can you measure the atomic radius of a noble gas such as Neon or Helium accurately? Would liquefaction help?
I heard that noble gases are the only common elements which have not been measured accurately as they don't bond with anything.
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1$\begingroup$ The underlying question: What is an atomic radius? I sort of remember something along the lines of "half the nuclear spacing in the molecule $\mathrm{X}_2$," which obviously doesn't work for all elements. $\endgroup$– user10851Commented Jul 5, 2014 at 10:43
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2 Answers
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I don't think anyone actually knows how to do this yet.
If you take a look at the atomic radius Wikipedia page, you'll notice that none of the noble gases have an experimental measurement for their radii. So what you heard was right to an extant. There are other elements that have not yet been measured as well.
The atomic radius of these gases can be predicted theoretically and their expected radii can be seen on this chem wiki page.
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You measure the atomic radius by calculating the distance of the atoms in the frozen state. This is also called van der Waals radius. Normally we take the half the distance of the atoms like Hydrogen. This is a complex equation you can find on the web.
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$\begingroup$ Welcome to SE.Physics! I edited out your background as it's customary to not rest on personal details in posts. If you wish to share more about your personal background, that can be done in your user profile. $\endgroup$– NatCommented Sep 30, 2018 at 1:04