Pronunciation: (är'gon), [key]
a colorless, odorless, chemically inactive, monatomic, gaseous element that, because of its inertness, is used for filling fluorescent and incandescent lamps and vacuum tubes. Symbol: Ar; at. no.: 18; at. wt.: 39.948.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.