What are nuclear fission and nuclear fusion?

Nuclear fission is the splitting of atomic nuclei and is used in nuclear reactors as a source of heat energy whichcan be transformed to electrical energy. Nuclear fusion is the joining together of atomic nuclei and is the process by which energy is released in
stars.

• to sketch a labelled diagram to illustrate how a chain reaction may occur.

• There are two fissionable substances in common use in nuclear reactors, uranium 235 and plutonium 239.
• Nuclear fission is the splitting of an atomic nucleus.
• For fission to occur the uranium 235 or plutonium 239 nucleus must first absorb a neutron
• The nucleus undergoing fission splits into two smaller nuclei and 2 or 3 neutrons and energy is released.
• The neutrons may go on to start a chain reaction.
• Nuclear fusion is the joining of two atomic nuclei to form a larger one.
• Nuclear fusion is the process by which energy is released in stars.