Difference Between Molecules and Compounds

Molecules vs Compounds

Atoms are the tiny units which collect up to form all the existing chemical substances. Atoms can join with other atoms in various ways and thus, form thousands of molecules. All elements have a diatomic or polyatomic arrangement to become stable except the Nobel gases. According to their electron donating or withdrawing abilities, they can form covalent bonds or ionic bonds. Sometimes, there are very weak attractions between atoms. Molecules and compounds are two words to distinguish between these large numbers of chemical substances. They can be present in solid, gaseous or liquid phase. They can be separated by chemical methods to yield the building elements or smaller units. Different molecules and compounds can be differentiated according to the size, weight and structural arrangements.


Molecules are made up by chemically bonding two or more atoms of the same element (e.g.: O2, N2) or different elements (H2O, NH3). Molecules don’t have a charge, and the atoms are bonded by the covalent bonds. Molecules can be very large (hemoglobin) or very small (H2), depending on the number of atoms that are connected. The type and number of atoms in a molecule are shown by the molecular formula. The simplest integer ratio of atoms present in a molecule is given by the empirical formula. For example, C6H12O6 is the molecular formula of glucose, and CH2O is the empirical formula. Molecular mass is the mass calculated considering the total number of atoms given in the molecular formula. Each molecule has its own geometry. The atoms in a molecule are arranged in the most stable manner with specific bond angle and bond lengths to minimize the repulsions and straining forces.


Compounds are a chemical substance made up by two or more different chemical elements. Combinations of two or more of the same chemical elements are not considered as compounds. For example, diatomic molecules like O2, H2, N2 or polyatomic molecules like P4 are not considered as compounds, but they are considered as molecules. NaCl, H2O, HNO3, C6H12O6 are some examples of common compounds. Therefore, compounds are a subset of molecules. The elements in a compound are joined together by covalent bonds, ionic bonds, metallic bonds, etc. The structure of the compound gives the number of atoms in the compound and their ratios. In a compound, elements are present in a definite proportion. We can find these details easily by looking at a chemical formula of a compound. Compounds are stable and they have characteristic shape, color, properties, etc.

What’s the difference between Molecules and Compounds?

- Molecules can be formed by joining the same or different elements, but compounds are formed only by joining different types of chemical elements.

- Compounds can be made by a combination of different molecules. In this case, a molecule is the smallest part of the compound. But the compound has different chemical and physical properties than the related molecule.

- In molecules, atoms are bonded by covalent bonds, and in compounds they can be bonded by ionic or metallic bonds other than the covalent bonds.