Last Updated: 20 March 2026Verified for JEE 2026
ChemistryJEE & NEET
Difference Between Atom and Molecule
Atoms are the smallest unit of an element, while molecules are formed when two or more atoms bond together. Understanding this distinction is fundamental to chemistry.
Atom vs Molecule — Comparison Table
| Aspect | Atom | Molecule |
|---|---|---|
| Definition | Smallest unit of an element | Two or more atoms bonded together |
| Existence | May or may not exist independently | Can exist independently |
| Composition | Protons, neutrons, electrons | Two or more atoms |
| Shape | Spherical | Various geometric shapes |
| Example | H, O, Na, Fe | H₂, O₂, H₂O, CO₂ |
| Reactivity | May be reactive | Can be stable or reactive |
| Visibility | Not visible even under microscope | Not visible (some large ones visible via electron microscope) |
Key Points to Remember
Noble gases exist as single atoms (monoatomic molecules)
Homonuclear molecules: same atoms (O₂, N₂)
Heteronuclear molecules: different atoms (H₂O, CO₂)
Molecular mass = sum of atomic masses of constituent atoms
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