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What Are Alpha, Beta, and Gamma Radiations?
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Meta title: Alpha, Beta, Gamma Radiation Explained
Meta description: Learn the differences between alpha, beta, and gamma radiation, their properties, and how they behave in IB Chemistry.
Alpha, beta, and gamma radiations are the three main types of nuclear radiation released during radioactive decay. These emissions help unstable nuclei become more stable. Understanding the differences between them is essential for IB Chemistry Topic 12 (Atomic Structure), particularly when studying nuclear equations, half-life, and radioactivity. Each type of radiation has unique characteristics, penetration abilities, and effects on matter.
What Is Nuclear Radiation?
When an unstable nucleus undergoes radioactive decay, it emits particles or energy. These emissions fall into three categories:
- Alpha particles (α)
- Beta particles (β⁻ or β⁺)
- Gamma rays (γ)
They differ in mass, charge, penetration power, and ionizing ability. These differences explain why they behave differently in electric fields, matter, and living tissues.
1. Alpha Radiation (α)
What is an alpha particle?
An alpha particle is a helium nucleus:
- 2 protons
- 2 neutrons
- Charge: +2
- Mass: 4 atomic mass units
Symbol: ⁴₂He or α
Key properties
- Heavy and slow-moving
- Highly ionizing (causes strong damage to cells)
- Low penetrating power: stopped by paper or human skin
- Travel only a few centimeters in air
When does alpha decay occur?
Alpha emission happens in very heavy, unstable nuclei such as:
- Uranium
- Radium
- Plutonium
Effect on the nucleus
Alpha decay reduces the mass number by 4 and atomic number by 2.
Example:
²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He
2. Beta Radiation (β)
Beta radiation comes in two forms:
- Beta-minus (β⁻)
- Beta-plus (β⁺)
Both involve changes within the nucleus but have different particles and effects.
Beta-minus (β⁻) Decay
What is emitted?
- A high-speed electron (β⁻)
- Charge: –1
- Very small mass
What happens in the nucleus?
A neutron converts to a proton, releasing an electron.
Effect on the nucleus
- Mass number stays the same
- Atomic number increases by 1
Example:
¹⁴₆C → ¹⁴₇N + β⁻
Properties
- Medium ionizing ability
- Greater penetration than alpha
- Stopped by aluminum foil or a few millimeters of metal
- Travels several meters in air
Beta-plus (β⁺) Decay
What is emitted?
- A positron (β⁺), the antiparticle of the electron
- Charge: +1
What happens?
A proton converts into a neutron, releasing a positron.
Effect on the nucleus
- Mass number stays the same
- Atomic number decreases by 1
Example:
¹¹₆C → ¹¹₅B + β⁺
Positrons quickly annihilate with electrons, releasing gamma radiation.
3. Gamma Radiation (γ)
What is gamma radiation?
Gamma radiation is:
- High-energy electromagnetic radiation
- No mass
- No charge
- Pure energy
Symbol: γ
When is it emitted?
Gamma emission occurs when a nucleus releases excess energy after alpha or beta decay.
Key properties
- Very high penetration: requires thick lead or concrete to block
- Low ionizing ability compared to alpha and beta
- Travels long distances in air
- No change to mass or atomic number
Effect on the nucleus
- Atomic number and mass number stay the same
- Only energy decreases
Example:
⁶⁰₂₇Co* → ⁶⁰₂₇Co + γ
(Asterisk indicates an excited state.)
Comparing Alpha, Beta, and Gamma Radiation
Radiation Mass Charge Penetration Ionizing Power Alpha Heavy (4 amu) +2 Low (paper stops it) Very high Beta Very light –1 or +1 Medium (metal foil) Medium Gamma None 0 Very high (lead/concrete) Low
This comparison is often tested in IB multiple-choice questions and nuclear equation problems.
Why These Differences Matter
These differences explain:
- How radiation affects human tissues
- How shielding is chosen for protection
- Why certain isotopes are used in medicine
- How nuclear equations are written and balanced
- How radioactive materials behave in the environment
Understanding each type’s mass, charge, and penetrating ability is foundational for nuclear chemistry.
FAQs
Why is alpha radiation so damaging but not deeply penetrating?
It is massive and highly ionizing, causing significant damage where it hits, but cannot travel far.
Which type is most dangerous outside the body?
Gamma radiation, because it penetrates deeply.
Which type is most dangerous inside the body?
Alpha radiation, due to extremely high ionizing power.
Can gamma rays change one element into another?
No—gamma rays only release energy; they do not alter proton number.
Conclusion
Alpha, beta, and gamma radiation represent three distinct ways unstable nuclei release energy and move toward stability. Alpha particles are heavy and highly ionizing, beta particles involve nuclear transformations, and gamma rays are pure energy with high penetration. Mastering these distinctions is essential for IB Chemistry, especially in nuclear reaction equations and radioactive decay problems.
