What is a Molecule?

Any person who will be reading this will be assumed as a studious and intelligent person… Intelligent and studious enough that it can be assumed that you already know about Atom.

If not, then please go and read about Atoms first because, without prior knowledge on atoms, you will be unable to understand Molecules.

A happy molecule!

When two or more Atoms come together, they are known as A Molecule.

In 1809, French chemist Joseph-Louis Gay-Lussac and others began doing several experiments with gases. These experiments were done by measuring the amounts of the gases that reacted.

Joseph Louis Gay-Lussac
Joseph Louis Gay-Lussac

In 1811, Amedeo Avogadro hypothesized that equal volumes of different gases, when at the same temperature and pressure, contained the same number of particles.

These experimental results and theories led to the determination of the number of atoms in substances. The name “molecule” was later given to particles made up of multiple atoms, which may be of the same or different atoms.

A molecule maybe –

  • Homonuclear– Molecule which consists of atoms of one chemical element. For example, Oxygen(O2)
  • Heteronuclear – A chemical compound composed of multiple elements. For Example, Water (H2O).

There are more classifications.

Types of molecules

  • Diatomic Molecules — A Molecule composed of two atoms are called Diatomic Molecules. These atoms can be of the same or different elements. O2 and CO are examples of diatomic molecules.
  • Heteronuclear Diatomic Molecules — A Molecule composed of two of atoms of the same elements combined is called a Heteronuclear Diatomic Molecule. There are seven diatomic elements and they are so reactive that they can be found very often bonded with another atom of the same type. They are-
  1. Hydrogen (H2)
  2. Nitrogen (N2)
  3. Oxygen ( O2)
  4. Fluorine ( (F2)
  5. Chlorine ( (Cl2),
  6. Iodine ( (I2)
  7. Bromine (Br2)
  • Homonuclear diatomic molecules –A Molecule which is composed of two atoms of different elements that are chemically combined is called a Homonuclear diatomic molecule. Examples of homonuclear diatomic molecules include Hydrogen Flouride (HF), hydrochloric acid (HCl), and carbon monoxide.

FUN FACT: Dalton incorrectly stated that atoms “hooked” together to form molecules. In 1808, Dalton published the famous diagram of combined “atoms”. Amedeo Avogadro created the word “molecule.

John Dalton
John Dalton

Now there is always confusion between a compound and a molecule. Also, this difference comes in exams more often than the other parts.

Difference between Compound & Molecule

So the difference between a compound and a Molecule is:

  • A molecule is formed when two or more atoms of an element join together chemically.
  • A compound is formed if the types of atoms are different from each other.
  • Not all molecules are compounds, since some molecules, such as oxygen gas (above image of molecule of-O2) or ozone (O3), consist only of one element or type of atom.

FUN FACT: Everything around you is made up of different kinds of molecules!


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