A molecule consists of group of atoms that are bonded together by chemical bond. It is the smallest particle of an element or a compound that has the properties of the element or the compound embedded in it. The atoms present in one element easily forms a bonding with the atoms of another element to form molecules. The size and complex nature of molecules varies hugely. Some molecules can have a single atom as is the case with helium, while in several other elements the number of atoms in the molecule can be more than one.