What is a chemical compound? Compounds are substances that are two or more elements combined together chemically in a standard proportion by weight. Compounds are all around us – they include familiar things, such as water, and more esoteric substances, such as triuranium octaoxide, the most commonly occurring natural source for uranium. This reference guide gives us a tour of 100 of the most important, common, unusual, and intriguing compounds known to science. Each entry gives an extensive explanation of the composition, molecular formula, and chemical properties of the compound. In addition, each entry reviews the relevant chemistry, history, and uses of the compound, with discussions of the origin of the compound’s name, the discovery or first synthesis of the compound, production statistics, and uses of the compound.