Types of Nuclear Reaction L3
1) Natural Radioactive Decay
A) Alpha Decay
B) Beta Decay
C) Proton Emission
D) Neutron Emission
E) Positron Emission
F) Orbital Electron Capture
2) Artificial Transmutation
3) Fission
4) Fusion
All nuclear reactions are accompanied by the emission of some level of Gamma
Radiation. Gamma Radiation has no charge and no mass.
It is energy similar to light that can penetrate up to 1 foot of lead, or 3 feet of concrete.
Natural Radioactive Decay
Definition: Spontaneous release of energy and particles from the nucleus.
The rate of a natural radioactive decay is measured in half-lives.
Alpha Decay
Definition: Release of alpha particles from the nucleus
Alpha particles have a +2 charge and a mass of 4 amu. They contain 2 p+ and 2 n0
making them identical to a Helium nucleus.
4
Symbols: He or 
2
Examples:
12
8
4
B  Li 
He
5
3
2
144
140
4
Nd 
Ce 
He
60
58
2
Alpha particles can be stopped by a sheet of paper.
Beta Decay
Definition: The breakdown of a nucleus by the release of a Beta Particle.
Beta Particles have a -1 charge and a mass of 1/1836 amu. They are a high speed
electron that is coming out of the nucleus.
0
e or 
Symbols:
1
Beta particles are produced by the breakdown of a neutron into a beta particle and a
proton. This results in an increase in the Atomic Number of the atom, but no change in
its Mass Number.
Examples:
11
11
0
Be 
B 
e
4
5
1
45
45
0
K 
Ca 
e
19
20
1
Beta particles can not penetrate more than a few inches into solid materials. They can
be stopped by 1/4 " of aluminum.
Proton Emission
Definition - the breakdown of the atom by the release of a proton.
This lowers both the Mass Number and Atomic Number by 1.
Example:
37
20𝐶𝑎
9
5𝐵
→
36
19𝐾
+ 11𝐻
→ 84𝐵𝑒 + 11𝐻
Neutron Emission
Definition – the breakdown of the atom by the release of a neutron.
This lowers the Mass Number by one, but does not change the Atomic Number. This
forms an isotope of the original atom.
Example:
9
3𝐿𝑖
16
6𝐶
→ 83𝐿𝑖 + 10𝑛
→
15
6𝐶
+ 10𝑛
Positron Emission
A positron is a particle with the same mass as an electron, but a +1 charge. It is the antimatter form of an electron. A positron is created by the splitting of a proton to form a
positron and a neutron. The positron is ejected from the nucleus and the neutron stays.
This reduces the Atomic Number by 1, but the Mass Number is unchanged.
Example:
186
77𝐼𝑟
→
186
76𝑂𝑠
20
11𝑁𝑎
→
20
10𝑁𝑒
+
+
0
+1𝑒
0
+1𝑒
Orbital Electron Capture
An electron in the lowest energy level is pulled into the nucleus where it combines with
a proton to form a neutron.
This causes a decrease in the Atomic Number by 1, but no change in the mass of the
atom.
Example:
125
54𝑋𝑒
20
11𝑁𝑎
+
+
0
−1𝑒
0
−1𝑒
→
→
125
53𝐼
20
10𝑁𝑒
Artificial Transmutation
Definition: Change in the nucleus of the atom due to its absorbing a particle
provided by scientists.
First produced by Rutherford (1919).
Example:
238
1
239
239
0
U  n 
U 
Np 
e
92
0
92
93
1
239
94
Pu 
0
1
e
Fission
Definition:
neutron.
Splitting of a large nucleus into 2 smaller nuclei by bombarding it with a
Example:
235
1
143
90
1
U  n 
Ba 
Kr  3 n  E
92
0
56
36
0
This process results in a small loss of mass. The mass is converted into energy (heat,
light and gamma radiation).
(E = mc2)
If the neutrons released by the reaction strike other U-235 atoms they will split those
atoms causing the reaction to continue resulting in a chain reaction.
Chain reaction - any self sustaining reaction
Uncontrolled Chain Reaction - If the chain reaction is allowed to continue at its own
pace the reaction speed increases rapidly resulting in an explosion. This is what
happens in a bomb.
Controlled Chain Reaction - A material is added that can capture neutrons, limiting the
number of additional atoms split. By adjusting the number of neutrons available to split
other atoms the rate of the reaction can be controlled. This is what happens in a nuclear
reactor.
Fusion
Definition - Joining of 2 small nuclei together to form a larger nucleus.
Example:
2
3
4
H  H 
He  n 0  E
1
1
2
This reaction requires temperatures above 1 million degrees Celsius. These
temperatures occur naturally in stars and at the center of an atom bomb explosion. The
Hydrogen bomb uses a sample of Hydrogen-2 and Hydrogen - 3 at the center of a
fission bomb. When the Plutonium - 239 explodes is heats the Hydrogen atoms while
driving them toward each other providing the energy needed for fusion to occur.
The fusion reaction results in a mass loss. The mass is converted to energy. Since the
mass loss in fusion is a higher percentage of the total mass present, the fusion reaction
gives off more energy than a fission reaction.
Stars due to their higher temperatures and pressures can utilize Hydrogen-1 in their
fusion reactions.
Research is underway to develop a way to run a controlled fusion reaction that we can
use to generate electricity.