In classic molecular theory, all matter is composed of smaller particles that retain the physical qualities of the whole. This is based on observations, especially noticeable in liquids, that inanimate substances can be divided, reshaped and possibly recombined in a manner that makes them indistinguishable from their original form. The division process can not be continued indefinitely however, and eventually a point is reach in which further division is impossible without altering the fundamental nature of the substance. The word "molecule" refers to the smallest indivisible particle of a compound. The study of chemistry further teaches that molecules can be further divided into "atoms" of chemical elements, of which 118 are currently known to exist.

An atom has electrical, magnetic, and gravitational properties which define how they react with other atoms in their vicinity.