Answer : Molecules.
Explanation : Elements are the class of pure substances that cannot be physically separated; but they are made up of the same atoms of the same elements. When two or more elements are combined chemically with a chemical bond they become physically inseparable; which is called as a Molecule. Therefore, the term which represents represents a pure substance that can be separated chemically, but cannot be separated physically, that is made up of two or more different atoms is a molecule.
A compound is made up many different molecules. The main difference between the compound and the molecule is that a compound must have at least two different elements. So, it can be said that a compound is a type of molecule.
Mixtures are made up of different compounds which can be physically separated.