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[hydro- + -gen]
SYMB: H A colorless, odorless, tasteless, gaseous chemical element, possessing one valence electron, atomic weight (mass) 1.0079, specific gravity 0.069, atomic number 1. A liter of the gas at sea level and at 0°C weighs 0.08988 g. There are three isotopes of hydrogen (protium, deuterium, and tritium), having atomic weights of approx. 1, 2, and 3, respectively.
CAS # 1333-74-0
Hydrogen is present in the sun and stars. Even though it is the most abundant element in the known universe, its concentration in the earth's atmosphere is only 0.00005%. Hydrogen occurs in its free state (in natural gases and volcanic eruptions) only in minute quantities. It occurs principally on the earth as water (hydrogen oxide, H2O) and is a constituent of all hydrocarbons. Hydrogen is present in all acids and in ionic form is responsible for the properties characteristic of acids. Hydrogen is present in nearly all organic compounds and is a component of all carbohydrates, proteins, and fats.
It is highly flammable and used in the oxyhydrogen flame in welding, in hydrogenation of oils for solidifying purposes, as a reducing agent, and in many syntheses.