Explain Nuclear Fusion with Example and Equation

Nuclear fusion is the phenomenon of fusing two or more lighter nuclei to form a heavy stable nucleus. It may release or absorb energy during the reaction process. Fusion between lighter nuclei releases energy whereas fusion between heavy nuclei requires supply of energy.

fusion reaction between deuterium and tritium

Examples of Nuclear Fusion

Some of the examples of nuclear fusion reaction which are also applicable to our daily life are:

  1. Solar energy from sun
    The light energy that we get from sun is the result of fusion reaction occurring inside it. There is the fusion of hydrogen nuclei into Helium nuclei along the production of solar(light) energy.
  2. Hydrogen bomb
    Hydrogen bomb are based on the principle of fusion reaction.
  3. Artificial fusion
    Some artificial fusion methods like thermonuclear fusion, inertial confinement fusion etc. are used to produce energy by facilitating fusion reaction.

Some Nuclear Fusion Equations

  • 1H1 + 1H11H2 + e+ + v + 0.42 MeV
  • 1H2 + 1H22He3 + n + 3.27 MeV
  • 1H2 + 1H21H3 + 1H1 + 4.03 MeV
  • 1H2 + 1H22He4 + 24 MeV
  • 41H12He4 + 2(+e0) + Q
  • 1H1 + 1H32He4 + 0n1 + Q

Read also: Difference between nuclear fission and fusion

Facts of Nuclear Fusion Reaction

Percentage of mass converted into energy is 1%.

It requires very high temperature(107-108K) and pressure. So, it is also called as thermonuclear reaction.

The energy released is very low as compared to fission.

But, energy released per unit mass in fusion is much larger than energy released per unit mass in fission.

The difference in masses of products and reactants is converted into energy. This difference in mass is called defect mass.

Protons are required for fusion.

This type of reaction occurs inside sun and stars.

FAQs on Nuclear Fusion

1)Where does nuclear fusion occurs?

Ans: It occurs inside sun, stars, man made hydrogen bomb and in artificial fusions. It generally occurs in very high temperature and pressure.


2)Where does nuclear fusion occurs in sun?

Ans: Fusion reaction occurs in the core region of sun. About 620 million metric tons of hydrogen nuclei(1H1) fuses to produce 616 million metric tons of helium (2He4) nuclei each second. This fusion reaction also releases energy in the form of light rays, electromagnetic radiation etc.

layers of sun

Image: Different layers of sun, Source: Kelvinsong

3)Why does nuclear fusion happen only in the sun’s core?

Ans: Inside sun’s core, there is abundant amount of hydrogen atoms present in free form. The core region of sun has very high temperature and pressure. These conditions favour the hydrogen nuclei to fuse into helium nuclei with production of huge amount of energy.

A chemical equation can be represented by proton-proton cycle as:
1H1 + 1H12H2 + +1e0 + Q1

1H1 + 1H22He3 + Q2

2He3 + 2He32He4 + 2(1H1) + Q3

The net reaction is given by

41H12He4 + 2(+1e0) + Q

Where Q=Q1+Q2+Q3, the total energy released during fusion of 4 hydrogen nuclei to form a helium nuclei. From above reaction it shows that 4 hydrogen nuclei fuses to produce 1 helium nuclei, 2 protons along with release of energy as byproducts.