ammonia vs. ammonium

a colorless, pungent, suffocating, highly water-soluble, gaseous compound, NH 3 , usually produced by the direct combination of nitrogen and hydrogen gases: used chiefly for refrigeration and in the manufacture of commercial chemicals and laboratory reagents.

Also called aqueous ammonia,. this gas dissolved in water; ammonium hydroxide.

the univalent ion, NH 4 + , or group, NH 4 , which plays the part of a metal in the salt formed when ammonia reacts with an acid.