Difference Between Atom and Molecule

Atom vs Molecule

The single elements are hardly stable under natural conditions. They form various combinations between them or with other elements in order to exist. When this happens, the properties of single elements vary and give rise to novel mixtures.


Atoms are the small building blocks of all existing substances. They are so tiny that we can’t even observe with our naked eye. Normally atoms are in the Angstrom range. Atom is made up of a nucleus, which has protons and neutrons. Other than neutrons and protons there are other small sub atomic particles in the nucleus, and there are electrons circling around the nucleus in orbitals. Most of the space in an atom is empty. The attractive forces between the positive charged nucleus (positive charge due to protons) and the negatively charged electrons maintain the atom’s shape.

Atoms of the same kind have similar protons and electrons. Same type of atoms may differ due to the number of neutrons present, and these are known as isotopes. Atoms can join with other atoms in various ways, 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.

Atom’s structure was determined by a series of experiments carried out by various scientists. According to the Daltons theory,

  • All matters are made out of atoms and atoms can’t be broken down further.
  • All atoms of a given element are identical.
  • Compounds are formed by the combination of two or more atoms.
  • Atoms cannot be made or destroyed. A chemical reaction is a rearrangement of atoms.

However, there are some modifications to the Daltons theory now with more advanced finding about the atom.


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 the 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 repulsions and the straining forces.

What is the difference between Atom and Molecule?

  • Atoms are single elements whereas molecules are two or more atoms combined together.
  • Molecules have bonds between atoms. They have intra-molecular and intermolecular forces, but atoms have interatomic forces only.
  • Molecule is usually stable by itself whereas atoms are not stable (except noble gases). Therefore, single atoms cannot be found in nature in contrast to molecules.