Pronunciation: (hī'dru-jun), [key]
a colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. Symbol: H; at. wt.: 1.00797; at. no.: 1; density: 0.0899 g/l at 0°C and 760 mm pressure.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.