1. Nuclear Reactions E = mc2
This states that energy and mass are the same ‘thing’
E = energy, Joules,J
m = mass, kilogrammes, kg
c = speed of light through air, 3.0 x108 ms-1

2. Example
Calculate the energy released if you could be turned into energy.
m = 75 kg, c = 3.0 x108 ms-1
E = m.c2
E = 75 x(3.0x108)2
E = 6.75x1018 J
This would keep a 40% efficient 750MW power station going for 114 years !

3. The Atom Particle Mass number Charge Symbol Proton 1 +1 Neutron
Electron 0* -1

4. Atomic and Mass Numbers
The total number of protons and neutrons in the nucleus is called the mass number, A.
The number of protons in the nucleus is called the atomic number, Z.
In a neutral atom the number of protons equals the number of electrons.

5. Alpha Decay
An unstable nucleus can emit an alpha or beta particle or a gamma ray and become more stable.
An alpha particle, α,is a Helium nucleus, 2 protons and 2 neutrons.
The mass and atomic no are conserved.

6. Beta Decay
A neutron in the nucleus can decay into a proton, ejecting an electron and an antineutrino.

7. Gamma Decay
There is NO change to the mass or atomic no. The nucleus does become more stable as excess energy is ejected.

8. Nuclear Fission and Fusion
Fission is the break up of a large nucleus into smaller fragments. It can be spontaneous or induced.
Fusion is when 2 small nuclei join together to form a larger nucleus.
In both cases there is a mass difference , this is turned into kinetic energy of the products ( E = m.c2 )

9. Energy From Fission and Fusion Example
Calculate the energy released in this induced fission reaction;
Given the following mass information:
particle
mass (kg) U
235 92
x 10-25 Cs
138 55
x 10-25 Rb 96 37
x 10-25 n 1
x 10-27

10. Energy From Fission and Fusion Example
Mass Before Reaction (Left Hand Side)
( x x 10-27) = x 10-25kg
Mass After Reaction (Right Hand Side)
( x x
(2 x x 10-27)) = x 10-25kg
Mass Difference = Mass Before – Mass After
= x – x = 2.65 x 10-28kg
Energy Released (E) = mc2
E = 2.65 x x (3 x 108)2 = x 10-11J

11. Energy From Fission and Fusion Example
This may seem very small but when we consider that 1kg of uranium contains about 2.56 x 1024 atoms,
then it has the potential to release as much energy as 2 million kilograms of coal.

12. Fusion
Hydrogen nuclei fuse together to form Helium in the sun, the same reaction takes place in a Hydrogen bomb.
The hope for the future is that Fusion reactors can be used to produce electrical energy.

13. Requirements
High temperatures of 100 million Kelvin are needed to ‘rip’ the electrons from atoms and form a plasma. Inducing an electrical current in the plasma is one way of achieving this.
The plasma needs to be contained by a magnetic field. If it touches the walls of the container it cools down.
The plasma needs to be confined for a long enough time for the particle density to reach a sufficiently high level so that more energy is given out than absorbed.