Difference Between Atom and Molecule

If you have remained attentive during your science classes in school, you must have heard your teacher speak about atoms and molecules. But the problem is that very few of you probably remember what these are.

Atom vs Molecule

The main difference between atom and molecule is that an atom happens to be the smallest particle in any element and also possesses the properties of the element. Breaking down an atom any further and retaining the properties of the element is not at all possible. Molecules, on the other hand, are the result of the combined efforts of two or more atoms.

Atom vs Molecule

One of the primary differences between molecules and atoms is that the former latter cannot be divided further like the former. An example of atom and molecules would be water.

It is a molecule with a combination of two atoms of hydrogen and one atom of oxygen.


Comparison Table Between Atom and Molecule (in Tabular Form)

Parameter of ComparisonAtomMolecule
DefinitionAn atom is the smallest and the most fundamental unit of any ordinary matter.Molecules comprise of two or even more atoms that are bound together by a chemical bond.
StructureAn atom is the smallest of all types of particles possessing the same properties as the element.Molecules are a combination of a minimum of two atoms.
Constituent ElementsIt constitutes protons, neutrons, and electrons.It constitutes a minimum of 2 atoms of the same element.
StabilityAtoms have electrons on the outer shell. Due to this fact atoms may not remain stable all the time.The formation of molecules take place to attain stability.
ReactivityAtoms of every element portray a certain degree of reactivity, except the noble elements.Compared to atoms, molecules are less reactive.
ExampleOxygen – OWater – H2O
Hydrogen – HPhosphorus – P4


What is Atom?

When you talk about an atom, it refers to the smallest particle in any ordinary matter that forms a chemical element. The air around you, anything liquid and solid are made up of either ionized or neutral atoms.

The normal size of an atom is around 100 picometers, which is approximately 1 in a millionth part of a millimeter.

Due to the extremely small size of atoms, it is not a simple task to predict their conduct with the help of classical physics. To predict and explain the behavior of atoms, experts use quantum principles.

You will find a nucleus in every atom along with a minimum of one electron that will be bound with the nucleus. In turn, this nucleus is comprised of a minimum of one proton and multiple neutrons.

Both the protons and the neutrons are collectively known as the nucleons and about 99.94% of the total mass of an atom is present in the nucleus.

The protons in an atom give out positive charges and the electrons give out negative charges. On the other hand, the neutrons have no charge at all.


What is Molecule?

When a minimum of two atoms are bound together with the help of chemical bonds it forms a molecule, which is electrically neutral by nature. Most of you may argue that molecules are ions that are almost similar to each other.

Well, there is a major difference between the two. Ions are electrically charged whereas, molecules are electrically neutral.

You will notice that molecules are not strictly used in organic chemistry, biochemistry, and quantum physics.

You need to remember that molecules may often be homonuclear. This means that a molecule may contain atoms from a single chemical element.

The best example of this is Oxygen or O2. It may also be heteronuclear, which means that it may contain atoms from different elements, such as water or H2O.

Make a note of the fact that atoms that are connected by any non-covalent interactions are not normally considered as one molecule. An example of this would be ionic bonds or hydrogen bonds.

Molecule 1

Main Differences Between Atom and Molecule

  1. An atom is the smallest particle of any element, whereas, a molecule is formed when two or more atoms are held together with the help of a chemical bond.
  2. It is possible for atoms to either exist or not exist independently. However, molecules always exist independently or in a free state.
  3. It is not possible to break down atoms any further. On the other hand, molecules can be broken down into atoms of either similar or different elements.
  4. The nucleus, comprising of neutrons and protons, along with electrons together form an atom. Molecules, on the other hand, comprise of a minimum of two atoms that may either be identical or different and held together by a chemical bond.
  5. Atoms are always shaped spherical ad molecules that may either be angular or rectangular or linear in shape.
  6. Atoms happen to be highly reactive. They can easily participate in any chemical reaction and do not decompose further into any subatomic particles. However, molecules are comparatively less reactive and do not participate in any chemical reaction.
Difference Between Atom and Molecule



Although both atoms and molecules are small in size and cannot be seen by the naked eye, it does not mean that both are similar in terms of properties.

Atoms are smaller of the two and also happen to be the building blocks of molecules. If you compare the size of atoms and molecules, you will find that atoms are smaller than molecules.

Since atoms are the building blocks of molecules it is not possible to break an atom into any subatomic particle. It is composed of a nucleus and electrons.

On the other hand, molecules can easily be broken down into atoms that may either be of the same element or different elements.

Due to the presence of electrons, atoms are electrically charged, whereas, comparatively, molecules are not electrically charged.

Even the shapes of atoms and molecules are different from each other.

Key Differences Between Atom and Molecule (PDF Format)

Download the key differences in .PDF format, to read or print them later:

Difference Between Atom and Molecule



  1. https://pubs.acs.org/doi/abs/10.1021/j100154a006
  2. https://aip.scitation.org/doi/abs/10.1063/1.1681085
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