A compound is a substance made up of two or more different elements that are chemically bonded together. The elements in a compound are present in a fixed ratio, and the properties of the compound are different from the properties of the individual elements. Examples of compounds include water (H2O), salt (NaCl), and carbon dioxide (CO2). Compounds can be classified as either organic or inorganic , depending on whether they contain carbon or not. Organic compounds typically contain carbon-hydrogen bonds, while inorganic compounds do not. Compounds can be formed through chemical reactions, where atoms of different elements bond together to form a new substance. These reactions can be represented by chemical equations , which show the reactants (the starting materials) on the left side of the equation and the products (the resulting compounds) on the right side. The number and type of atoms on each side of the equation must be the same, as req...