Difference between Molecules and Compounds

Molecule

A molecule is a group of two or more atoms that are joined together, showing the smallest identifiable unit where the pure substance can hold its compositions chemical properties. The atoms in molecules may contain the same chemical element or different chemical elements. If the atoms consist same chemical element, then it is called homonuclear like Oxygen.  Whereas, if atoms consist different chemical elements, then it is called heteronuclear like water or nitrogen oxide.

The different types of molecules which are based on the number of atoms per molecule are:

• Diatomic molecules- it is made up of two atoms. For instance, HCI consists of one hydrogen atom joined with one chlorine atom.
• Triatomic molecules- it is made up of three atoms. For instance, CO2 consist of one carbon atom joined with two oxygen atoms.
• Polyatomic molecules- it is made up of three or more atoms held together by covalent bonds. For instance, NH3 consists of one nitrogen atom joined with three hydrogen atoms.

Molecules can be categorized into two types of chemical bonds:

• Covalent molecules
• Ionic molecules

Molecules example are CO2, NO2, HCI, N2, S8, CO Etc.

Compound

Compounds are group of two or more elements chemically unite together in a fixed proportion by the chemical bond. Compounds can be categorized into three types of chemical bonds containing the atoms together:

• Molecules are joined together by a covalent bond.
• Ionic compounds are joined together by an ionic bond.
• Intermetallic compounds are joined together by metallic bonds.

Chemical formula

A chemical formula classifies compounds. For instance, the chemical formula of water is H2O; it shows that two atoms of hydrogen and one atom of Oxygen are joined together to give one molecule of H2O. Therefore, heteronuclear molecules are classified as compounds.   

Compound examples are H2O (water), C2H4O2 (acetic acid), NaCl (common salt or sodium chloride), etc.

Comparison between molecules and compounds

Basis	Molecules	Compound
Meaning	A molecule is a group of two or more atoms that are joined together, showing the smallest identifiable unit where the pure substance can hold its compositions chemical properties of the substance.	Compounds are a group of two or more elements chemically unite together in a fixed proportion by the chemical bond.
Properties	Includes chemical properties, physical properties, and structural properties of molecules.	Compounds are entirely different from the properties of its constituent.
Relatedness	All molecules are not compounds.	All compounds are molecules.
Visualness	Molecules cannot be seen with an unaided eye as they are at the atomic level.	Compounds can be clearly seen with the unaided eye
Structure	Molecules are groups of atoms joined together by a strong force.	All compounds are actual matter in their complete shape.
Stability	Molecules can be unstable.	Compounds are always stable as they are in a physical form.
Type of chemical bonds	Molecules can be of ionic bonds or covalent bonds	Compounds can be ionic bonds, covalent bonds, or metallic bonds.
Example	An example of molecules is Oxygen, water, ozone, etc.	An example of compounds is acetic acid, water, sodium chloride, etc.