Helium compounds

Class of extreme chemical compounds

Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly assumed that helium compounds could not exist at all, or at least not under normal conditions. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, and in this form the atom does not readily accept any extra electrons nor join with anything to make covalent compounds.

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