Question

The splitting of a heavy nucleus into lighter nuclei is known as

• A. fusion
• B. fission
• C. rusting
• D. combustion

Answer 1

The correct option is B

fission

Explanation for the correct option

Option B: fission

1. When the nucleus of a heavy atom, like uranium is struck by a neutron, it splits into two nuclei of lighter elements. In this process, large quantities of energy are released.
2. Two or more neutrons are also liberated during this process. These neutrons in turn split other uranium nuclei and more energy is released.
3. This process continues in the form of a chain reaction releasing a tremendous amount of energy.
4. Such an uncontrolled chain reaction takes place in an atomic bomb. The splitting of heavy nuclei like uranium into lighter nuclei is known as nuclear fission.

Explanation for the incorrect options

Option A: fusion

1. In nuclear fusion, small nuclei fuse to form a large nucleus.
2. The source of energy of the sun is fusion.
3. On the surface of the sun, hydrogen atoms combine to create helium atoms at very high temperatures and pressure.
4. During fusion, a tremendous amount of energy is liberated and it is even more than the energy released during fission. Scientists are trying to develop technologies to carry out this fusion reaction in a controlled manner.
   

Option C: rusting

1. Corrosion of iron is called rusting.
2. Rusting is a process in which iron metal reacts with moist air (water + oxygen) present in the atmosphere to form iron oxide,${\mathrm{Fe}}_2{\mathrm{O}}_3$, which is reddish brown.
3. Rusting of iron leads to very heavy damage to the substance.
4. Thus, it should be prevented by applying oil, grease or paint to iron objects that can prevent rusting to some extent.
5. Electroplating or galvanizing iron objects prevents them from rusting.

Option D: combustion

1. A chemical process in which a substance reacts with oxygen to give off heat and light is called combustion.
2. The combustion of fossil fuel produces carbon dioxide which is released in the atmosphere. Carbon dioxide has the tendency to absorb infrared radiation resulting in the warming of the earth's atmosphere. This is called the greenhouse effect.
3. Combustion of fossil fuels in an insufficient supply of oxygen forms carbon monoxide which is poisonous. When inhaled, it may cause suffocation or even death.

Thus, the splitting of a heavy nucleus into lighter nuclei is known as nuclear fission.
Hence, option (B) is correct.