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And here I was, thinking helium was the tiniest atom unless you start counting cations which has it beaten by Li+ and He+
by bjoli 2y ago
And here I was, thinking helium was the tiniest atom unless you start counting cations which has it beaten by Li+ and He+
- adrian_b 2y agoYes, at the same number of electrons, the heavier atoms have a smaller volume, i.e. they are tinier, because their greater nuclear charge attracts the electrons closer to the nucleus. Li+, Be++, B+++ are tinier than He, but they are ions, not neutral atoms. Neutral Li, Be, B are bigger than He, because they have an additional electron layer. Both neutral H and H- are bigger than He, because their one or two electrons are attracted less by a proton than by a He nucleus with double charge. H+ is just a bare proton, so it is orders of magnitude smaller than any other ion, but it is not a neutral atom. So He is indeed the smallest neutral atom.
- addaon 2y agoMuonic atoms are many, many times smaller, and neutral — so small that the reduction in atomic radius by substituting a muon for an electron can catalyze fusion. Purely muon helium would be the smallest such. (Tauons can’t form atoms as their decay time is shorter by orders of magnitude than would be needed.)
- adrian_b 2y agoYou are right, so in order to say that the helium atom is the tiniest, the statement should be additionally qualified, by saying that it is the tiniest among the stable neutral atoms, in order to exclude the muonic atoms.