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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] Helium's first ionization energy of 24.57 eV is the highest of any element. [2]
Triatomic hydrogen, H 3, is unstable and breaks up spontaneously. H 3 +, the trihydrogen cation is stable by itself and is symmetric. 4 He 3, the helium trimer is only weakly bound by van der Waals force and is in an Efimov state. [1] Trisulfur (S 3) is analogous to ozone.
Many elements can combine to form heteronuclear diatomic molecules, depending on temperature and pressure. Examples are gases carbon monoxide (CO), nitric oxide (NO), and hydrogen chloride (HCl). Many 1:1 binary compounds are not normally considered diatomic because they are polymeric at room temperature, but they form diatomic molecules when ...
Atomicity is the total number of atoms present in a molecule of an element. For example, each molecule of oxygen (O 2) is composed of two oxygen atoms. Therefore, the atomicity of oxygen is 2. [1] In older contexts, atomicity is sometimes equivalent to valency. Some authors also use the term to refer to the maximum number of valencies observed ...
Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N 2) 11) crystals have been grown at room temperature at pressures ca. 10 GPa in a diamond anvil cell. [130] The insulating electride Na 2 He has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite ...
Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest element and, at standard conditions, is a gas of diatomic molecules with the formula H 2, sometimes called dihydrogen, [11] hydrogen gas, molecular hydrogen, or simply hydrogen. It is colorless, odorless, [12] non-toxic, and highly combustible.
Oxygen is present as compounds in the atmosphere in trace quantities in the form of carbon dioxide (CO 2) and oxides of nitrogen (NO x). The Earth's crustal rock is composed in large part of oxides of silicon (silica SiO 2, found in granite and sand), aluminium (aluminium oxide Al 2 O 3, in bauxite and corundum), iron (iron (III) oxide Fe 2 O
Helium is also used as filling gas in nuclear fuel rods for nuclear reactors. [88] Goodyear Blimp. Since the Hindenburg disaster in 1937, [89] helium has replaced hydrogen as a lifting gas in blimps and balloons: despite an 8.6% [90] decrease in buoyancy compared to hydrogen, helium is not combustible. [13]