6. Physical reaction
Involves a change in the nucleus of an atom
Two types –Fission and fusion.
Source – Mass of the nucleus
Released mainly in the form of heat energy
Known as atomic energy
7. 17Cl35 + 0n1 15P32 + 2He4 + High energy
When Uranium 235 atoms are bombarded with slow
moving neutrons,the heavy uranium nucleus breaks up
to produce two medium-weight atoms ,neutrons and a
tremendous amount of energy.
235 + 0n1 139 + 94 + 30n1 + High energy
92 56Ba 36Kr
10. Fission means ‘to split’
German scientist otto hann and strassman
discovered that when a 92U235 nucleus is bombarded
by thermal neutrons,it splits up into two smalller
nuclei of barium and Krypton along with the release
of three neutrons
The process in which the heavy nucleus of a radioactive
atom (such as uranium,thorium and plutonium) splits up
into smaller nuclei when bombarded with low energy
neutrons is known as nuclear fission.
12. The sum of masses of the smaller nuclei formed in a
fission reaction is a little less than that of the mass of the
original heavy nucleus
So,there is a small loss of mass in the nuclear fission
This energy is used for generating electricity.
13. Neutrons may:
1 - Cause another fission by colliding with a U235 nucleus
• Creates two smaller nuclides and free neutrons
• The free neutrons potentially collide with nearby U235 nuclei
• May cause the nuclide to split as well
Each split (fission) is
accompanied by a
large quantity of E-N-
14. Chain reaction
When the neutrons in the fission reaction continuously
bombard with heavy nuclei then , a continuous self
sustaining nuclear chain reaction happens.
Sometimes,I t becomes uncontrolllable and that is
the atom bomb.
To control it boron rods are used because boron has
the property to absorb neutrons.
A large nucleus splits into several
small nuclei when impacted by a
neutron, and energy is released in
Several small nuclei fuse
together and release
Produces tremendous energy from a small amount
of nuclear fuel.
Once the nuclear fuel is filled,the plant can go for
Does not produce greenhouse gases like CO2
Difficult to dispose the radioactive waste from the
nuclear fission reaction.
Risk of accidents in Nuclear reactors
High cost of installation of nuclear power plants
and limited availability of uranium.