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Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium. [68] About 0.9% of the Sun 's mass is oxygen. [ 19 ] Oxygen constitutes 49.2% of the Earth's crust by mass [ 69 ] as part of oxide compounds such as silicon dioxide and is the most abundant element by mass in the Earth's crust .
Its bulk properties partly result from the interaction of its component atoms, oxygen and hydrogen, with atoms of nearby water molecules. Hydrogen atoms are covalently bonded to oxygen in a water molecule but also have an additional attraction (about 23.3 kJ·mol −1 per hydrogen atom) to an adjacent oxygen atom in a separate molecule. [2]
About 99% of the Earth's atmosphere is composed of two species of diatomic molecules: nitrogen (78%) and oxygen (21%). The natural abundance of hydrogen (H 2) in the Earth's atmosphere is only of the order of parts per million, but H 2 is the most abundant diatomic molecule in the universe. The interstellar medium is dominated by hydrogen atoms.
An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. [1] The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.
The hydroperoxyl radical, also known as the hydrogen superoxide, is the protonated form of superoxide with the chemical formula HO 2, also written HOO •. This species plays an important role in the atmosphere and as a reactive oxygen species in cell biology.
Its chemical formula, H 2 O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. [21] In liquid form, H 2 O is also called "water" at standard temperature and pressure.
Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...
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.