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In acid-base theory, hydrogen is able to become the $\ce{H+}$ ion, or a bare proton. I'm curious if other, larger atoms can have their electrons stripped to the point of being only a nucleus. I know helium can in the form of an alpha particle, but are there any other examples? For example, could you have $\ce{Li^3+}$?

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    $\begingroup$ While technically it is true, in real chemical environment the H+ is never a solo proton going around: it is always attached to something (solvent or other molecules). The reason is the a bare proton (or other nucleus) would be very unstable energetically, and strongly polarize its environment. $\endgroup$ – Greg Apr 6 '17 at 14:47
  • $\begingroup$ chemistry.stackexchange.com/questions/41997/… $\endgroup$ – Mithoron Apr 6 '17 at 16:02
  • $\begingroup$ Only in the low pressure gas phase it is possible to strip all the electrons off atoms, and as pointed out by @Greg ions in solution are always going to be solvated, which true also of the electron. $\endgroup$ – porphyrin Apr 6 '17 at 19:53
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The fact that ionization energies have been measured for many single-electron ions is clear proof that bare nuclei, other than the examples mentioned in the question, have been produced. However, some might say that the process of ionization is more of a physical than a chemical one. This distinction is left to the reader.

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    $\begingroup$ In the atomic physics community, they are 'fully stripped' nuclei. Sending energetic ions through thin foils under the right conditions will result in some fraction of fully stripped ions, which can then be magnetically separated out from the other charge states. But, yes, it isn't chemistry. $\endgroup$ – Jon Custer Apr 6 '17 at 16:02
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The most common bare-nucleus species on Earth is actually not $\ce {H+} $. It's $\ce {He^{2+}} $, better known as $\alpha $ particles produced by radioactive decay. These $\alpha $ particles do not have a very long shelf life, as they will rapidly take up electrons to become just plain helium. But they are real enough for household smoke detectors to rely on them or at least their (ionized) reaction products obtained by taking up said electrons.

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