Children's, Intermediate and Advanced Online English Dictionary & Thesaurus

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heavy hydrogen an isotope of hydrogen with a mass number greater than one; deuterium.
hydrogen bomb a very powerful type of bomb. When its hydrogen atoms are forced together under great heat and pressure, they release energy in a huge explosion.
hydrogen ion the positive ion of a hydrogen atom whose electron has been removed, as in acids.
hydrogen peroxide an unstable compound of hydrogen and oxygen whose water solution is used mostly as an antiseptic or bleach.
hydrogen sulfide a poisonous, colorless gas that has the odor of rotten eggs and is used mostly in chemical manufacturing and metallurgy.