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Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. [1]
Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds. Under high pressures helium can form compounds with various other elements.
The noble gases (helium, neon, argon, krypton, xenon and radon) were previously known as 'inert gases' because of their perceived lack of participation in any chemical reactions. The reason for this is that their outermost electron shells (valence shells) are completely filled, so that they have little tendency to gain or lose electrons.
An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. Though inert gases have a variety of applications, they are generally used to prevent unwanted chemical reactions with the oxygen ( oxidation ) and moisture ( hydrolysis ) in the air from ...
Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen. Rockets need to achieve specific speeds and ...
A non-combustible material [17] is a substance that does not ignite, burn, support combustion, or release flammable vapors when subject to fire or heat, in the form in which it is used and under conditions anticipated. Any solid substance complying with either of two sets of passing criteria listed in Section 8 of ASTM E 136 when the substance ...
The inertness of noble gases makes them useful whenever chemical reactions are unwanted. For example, argon is used as a shielding gas in welding and as a filler gas in incandescent light bulbs. Helium is used to provide buoyancy in blimps and balloons. Helium and neon are also used as refrigerants due to their low boiling points.
The stable cation [HeH] + was reported in 1925, [24] but was not considered a true compound since it is not neutral and cannot be isolated. In 2016 scientists created the helium compound disodium helide (Na 2 He) which was the first helium compound discovered. [25]