An element is a simple substance that is made from one type of atom and cannot be broken down into simpler components by chemical or physical means. A mixture is made from two or more substances that are chemically different and are not chemically joined. A compound is a substance formed when two or more elements chemically react with each other to form chemical bonds between their atoms.
Compounds can be classified as pure substances because each element that formed it is in fixed proportions; therefore it has a definite chemical composition. Mixtures are considered impure substances because no new substance is formed, therefore they do not have any fixed properties. The properties of a mixture are dependent on the individual components that formed it and the ratio with which they combined.
The components of a compound can only be separated using chemical methods. The constituents of a mixture can be separated using physical methods. For example, a mixture of copper and phosphorus can be separated using a magnet but the same cannot be done for copper phosphide. A common example of a mixture is air. Carbon dioxide is a good example of compound. All the elements known to man are listed in the periodic table.