Radioactive decay occurs through three main types: alpha decay, beta decay, and gamma decay. Alpha decay involves emitting an alpha particle, which is identical to a helium nucleus containing two protons and two neutrons. Beta decay results in one less neutron but one extra proton. Gamma decay occurs when atoms are still energetic after alpha or beta decay and emit gamma rays to become stable. These decays are important applications in areas like nuclear medicine, nuclear reactors, and sterilization.

1. RADIOACTIVE
DECAYS
Alpha, Beta, and Gamma Decay

2. Outline
• Radioactive decays
• Alpha Decay
• Beta Decay
• Gamma decay
• Applications
• Summary

3. Introduction
The atom consists of two parts:
1. The nucleus which contains:
2. Orbiting electrons.
protons
neutrons

4. All matter is made up of elements (e.g. carbon,
hydrogen, etc.).
The smallest part of an element is called an atom.
. Atom of different elements contain different numbers of
protons
The mass of an atom is almost entirely due to the
number of protons and neutrons.

5. X
A
Z
Mass number
Atomic number
Element symbol
= number of protons + number of neutrons
= number of protons

6. X
A
Z
A = number of protons + number of neutrons
Z = number of protons
A – Z = number of neutrons
Number of neutrons = Mass Number – Atomic Number

7. Radioactive decay results in the emission of either:
• an alpha particle (α),
• a beta particle (β),
• or a gamma ray(γ).
Radioactive Decay

8. An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.
Alpha Decay

9. X
A
Z
Y
A - 4
Z - 2
+ He
4
2
unstable atom
more stable atom
alpha particle

10. Ra
226
88
Rn
222
86
He
4
2

11. X
A
Z
Y
A - 4
Z - 2
+ He
4
2
Ra
226
88
Rn
222
86
+ He
4
2

12. Beta Decay
As a result of beta decay, the nucleus has one less
neutron, but one extra proton.
The atomic number, Z, increases by 1 and the mass
number, A, stays the same.

13. Po
218
84
β
0
-1
At
218
85

14. X
A
Z
Y
A
Z + 1
+ β
0
-1
Po
218
84
Rn
218
85
+ β
0
-1

15. Gamma Decay
Gamma rays are electromagnetic radiation with
high frequency.
When atoms decay by emitting α or β particles to
form a new atom, the nuclei of the new atom
formed may still have too much energy to be
completely stable.

16. Applications
• Nuclear Medicine.
• Used and produce in nuclear reactor.
• Used to sterilize medical instruments and food

17. Summary
• Unstable atomic nucleus having atomic mass
greater than 82 becomes stable by emitting alpha
particle, beta particle or gamma rays.
• These three decay are alpha, beta and gamma