<P> A compound can be converted to a different chemical composition by interaction with a second chemical compound via a chemical reaction . In this process, bonds between atoms are broken in both of the interacting compounds, and then bonds are reformed so that new associations are made between atoms . Schematically, this reaction could be described as AB + CD -> AD + CB, where A, B, C, and D are each unique atoms; and AB, AD, CD, and CB are each unique compounds . </P> <P> A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved . Examples are the diatomic molecule hydrogen (H) and the polyatomic molecule sulfur (S). </P> <Table> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> Pure water (H O) is an example of a compound: the ball - and - stick model of the molecule (above) shows the spatial association of two parts hydrogen (white) and one part (s) oxygen (red) </Td> </Tr> </Table> <Tr> <Td_colspan="2"> Pure water (H O) is an example of a compound: the ball - and - stick model of the molecule (above) shows the spatial association of two parts hydrogen (white) and one part (s) oxygen (red) </Td> </Tr>

A compound is formed by two positive elements