A chemical combination of atoms of different elements to form a substance in which the ration of combining atoms remains fixed and is specific to that substance. The existence of a compound does not necessarily imply that it is stable.
Many compounds have lifetimes less than a second.
Electrons are present in all atoms in shells around the nucleus. The formula of a compound showing the simplest ratio of the atoms present. An atom or molecule that has a negative or positive charge as a result of losing or gaining one or more electrons. The positive and negative ions are arranged in definite patterns and are held together by electrostatic attraction. Common examples are sodium chloride and cesium chloride.