What is nuclear fission? Name the substance used for it. Write one fission reaction.

Nuclear fission is the process in which a heavy nucleus splits into two lighter nuclei of nearly the same size, when bombarded with slow neutrons. In each fission reaction, a tremendous amount of energy is released.

Uranium is one substance that can be used for nuclear fission.

Example of fission reaction is —

$\begin{matrix} _{92}^{235}\text{U} & + & _{0}^{1}\text{n} & \longrightarrow & (_{92}^{236}\text{U}) & \longrightarrow & _{56}^{144}\text{Ba} \ \footnotesize{\text{(uranium)}} & & \footnotesize{\text{(neutron)}} & & & & \footnotesize{\text{(barium)}} \ & + & _{36}^{89}\text{Kr} & + & 3 \space _{0}^{1}\text{n} & + & \text{energy} \ & & \footnotesize{\text{(krypton)}} & & \footnotesize{\text{(neutrons)}} \end{matrix}$