An atom is the smallest unit of matter. It is made up of fundamental particles like protons, neutrons, and electrons. It is unstable and cannot exist freely. On the other hand, a molecule is a combination of two or more atoms with the help of bonding. This bonding can either be covalent or ionic.
Atom vs Molecule
| Atom | Molecule |
| It is the smallest particle of an element | It is the combination of two or more atoms |
| They are building blocks of molecules | They are building blocks of compounds |
| It consists of protons, neutrons, and electrons | It is made up of several atoms (same or different) |
| Atoms are less stable | Molecules are more stable |
| They cannot exist freely | They can exist freely |
| Atom is not breakable | A molecule can be broken down into its constituent atoms |
| Atoms have spherical shape | Molecules may have linear or angular shapes |
| They are more reactive | They are less reactive |
| They have more energy | They have less energy |
| Examples of atoms are H, O, Xe, Kr, etc |
Examples of molecules are I2, Cl2, O2, H2, etc |
Explanation of atom
The Greek scientist Democritus ( 460-370 B.C ) said that atoms are building blocks or smallest particles of matter. He also believed that atoms are uniform, incompressible solids, hard and that they are indestructible. The word ‘atom’ is derived from the Greek word “atomos”, which means indivisible. This evidence of Democritus was based on theoretical research.
In the late 17th century, a quantitative study led by Antoine Lavoisier and his coworkers disclosed that elements were the components of many different substances. It was also investigated how elements combined to form compounds and how these compounds can be broken down into their constituent elements. Later in 1808, John Dalton recognized that matter is composed of atoms of different elements. They have differences in their physical and chemical properties.
Further development came when Swedish chemist, Jons Jacob Berzelius determined the atomic masses of elements. A number of his values are close to the modern values of atomic masses. He also introduced the symbol system for elements.
Modern research of atoms shows subatomic particles like proton, neutron, electron, hyperon, neutrino, and antineutrino. etc. More than a hundred particles are thought to exist in an atom. However, electrons, protons, and neutrons are regarded as fundamental particles of atoms.
Explanation of Molecules
In 1926, Jean Perrin, a French physicist, received a noble prize for proving the existence of molecules. He accomplished such a marvelous discovery by studying Avogadro’s number in liquid state systems.
A molecule is the smallest particle in an element or a compound. They are made up of atoms held together by chemical bonds. Depending upon the difference in nature of these atoms, a bond is decided to be polar or non-polar.
A molecule is a group of two or more atoms that are chemically combined. There are two types of molecules.
- Diatomic molecules
- Polyatomic molecules
Diatomic molecules
When two atoms come close to each other and combine via a covalent bond, the resulting molecule is a diatomic molecule.
For example
- Hydrogen (H2)
- Oxygen (O2)
- Chlorine (Cl2)
- Nitrogen (N2)
- Fluorine (F2), etc
Polyatomic molecules
When more than two atoms combine together, polyatomic molecules are formed. They are large molecules, hence, they are more stable.
For example
- Carbon dioxide (CO2)
- Water (H2O)
- Ozone (O3)
- Sulfur (S8)
- Phosphorus (P4), etc
Atoms vs Molecules: Key Difference(s)
- Atoms are single, unbreakable particles of matter, regarded as building blocks of everything that is present.
- Molecules are the next unit of matter (existence). They are also the building blocks, but not for matter. They are the building blocks of elements and compounds.
- It is the molecules, where the concepts like intermolecular forces hold and strengths are taken into account. Whereas, atoms only have electrostatic forces. Joining these atoms requires intramolecular forces i.e. bonds.
Concepts Berg
When to use molecules?
Molecules are made up of atoms. All living and nonliving things are composed of molecules. They have important roles in our lives. For example, giant protein structures are made up of molecules.
What is the difference between atom, molecule, and compound?
Atoms and molecules are the basic units of matter. Atoms are the smallest particles. When a group of atoms combines together, they form molecules. Compounds are formed as a result of the union of elements or molecules.
Nitrogen gas is an atom or a molecule?
Nitrogen exists in the form of molecule N2.
What are the similarities between atoms and molecules?
Both atoms and molecules:
- contain protons, electrons, and neutrons
- have the same arrangements of charged particles
- are building blocks of matter
What is the difference between a photon and an atom?
Photons are the units of electromagnetic waves, also called packets of energy. On the other side, an atom is the smallest particle of an element that contains fundamental particles like protons, electrons, and neutrons.
A photon represents a wave whereas, an atom represents matter.
What’s the difference between a hydrogen atom and a hydrogen molecule?
H is an atom while H2 is a molecule. The hydrogen atom is not stable and cannot exist freely while the hydrogen molecule can exist independently.
What is the difference between an ion and a molecule?
Ion is a charged species. There are two types of ions: anions and cations. Whereas, a molecule is neutral species.
What is the difference between cells and atoms?
Cells are made up of atoms. It is a terminology that is used in biology. Cells have larger sizes. They contain organelles while atoms contain fundamental particles.
Which will have a greater entropy, an atom or a molecule?
Molecules have more possible configurations like vibrational, rotational, and translational. So it has more entropy than an atom.
References
- Difference Between Atom and Molecule (toppr.com)
- Atoms, Molecules, and Compounds (manoa.hawaii.edu)
- Atom vs. Molecule (byjus.com)
