The atom and atomic structure is constantly under study and has revealed a whole new array of subatomic particles. To date, a new definition for atom has not been developed. Elements and compounds may exist together without form-ing new compounds. Their atoms do not combine. This is known as a mixture.
Air is a familiar mix-ture.
Ocean water, too, is another mixture, made up chiefly of water and salt molecules, with a smaller number of molecules of many other com-pounds as well as molecules of several elements. Solids are substances that have a definite volume and shape and retain their original shape and volume after being moved from one container to another, such as a block of wood or a stone. A liquid has a definite volume, because it is almost impossible to put it into a smaller space. However, when a liquid is moved from one container to another, it retains its original volume, but takes on the shape of the container into which it is moved. For example, if a glass of water is poured into a larger bucket or pail, the volume remains unchanged.