Answer:
The main difference between an atom and a molecule lies in the size: while the atom is the smallest unit into which matter can be divided into any of its states, a molecule is the union of a group of atoms, that is, this composed of several atoms. Thus, for example, a water molecule is composed of two hydrogen atoms and one oxygen atom (H2O). Therefore, it can be said that atoms are the smallest unit in which the chemical elements of the world can be divided, while molecules are the particles of matter that are formed through the combination of these elements.