CBSE Class 10 Answered

Nuclear Fission

is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing free neutrons and other smaller nuclei, which may eventually produce photons (in the form of gamma rays).

Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments

Fission is a form of elemental transmutation because the resulting fragments are not the same element as the original atom.

Nuclear fusion

Is the process by which multiple atomic particles join together to form a heavier nucleus. It is accompanied by the release or absorption of energy

The fusion of two nuclei lighter than iron generally releases energy while the fusion of nuclei heavier than iron absorbs energy; vice-versa for the reverse process, nuclear fission.

It takes considerable energy to force nuclei to fuse, even those of the lightest element, hydrogen. This is because all nuclei have a positive charge (due to their protons), and as like charges repel, nuclei strongly resist being put too close together.