Explain Radioactivity With Equation and Comparison, Alpha Beta , Gamma

Radioactivity is a nuclear phenomenon in which an unstable atomic nucleus spontaneously emits radiation and transforms into a more stable nucleus. This process is known as radioactive decay.

Discovery of Radioactivity

Radioactivity was discovered accidentally by A. H. Becquerel in 1896. While studying the fluorescence and phosphorescence of uranium compounds, he observed that uranium emitted invisible radiations capable of penetrating black paper and silver, causing the blackening of a photographic plate.

What is Radioactivity?

Radioactivity is the spontaneous disintegration of an unstable atomic nucleus accompanied by the emission of energetic particles or electromagnetic radiations.

Key Characteristics of Radioactivity

• It is a spontaneous process.
• It is a nuclear phenomenon.
• It is independent of temperature and pressure.
• It is unaffected by chemical reactions.
• It results in the emission of α, β, or γ radiations.

Types of Radioactive Decay

1. Alpha (α) Decay

In alpha decay, a helium nucleus (α-particle) is emitted from the radioactive nucleus.

Alpha Particle: ⁴₂He

• Charge = +2e
• Mass Number = 4
• Atomic Number = 2

General Equation

A_ZX → A-4_Z-2Y + ⁴₂He

Example

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

Here, Uranium-238 emits an alpha particle and transforms into Thorium-234.

2. Beta (β) Decay

In beta decay, electrons (β⁻) or positrons (β⁺) are emitted from the nucleus.

Types of Beta Decay

• β⁻ Decay (Electron Emission)
• β⁺ Decay (Positron Emission)

• Charge = -e or +e
• Very small mass
• High speed

General Equation

A_ZX → A_Z+1Y + e⁻

Example (β⁻ Decay)

¹⁴₆C → ¹⁴₇N + e^- + ν̅

Here, Carbon-14 emits a beta particle (electron) and transforms into Nitrogen-14.

3. Gamma (γ) Decay

In gamma decay, high-energy photons known as gamma rays are emitted by an excited nucleus.

• No charge
• No mass
• Highest penetrating power
• Travel at the speed of light

General Equation

A_ZX* → A_ZX + γ

Example

⁶⁰₂₇Co* → ⁶⁰₂₇Co + γ

Here, excited Cobalt-60 emits a gamma ray and reaches a lower energy state.

Comparison of α, β and γ Radiations

Property	α-rays	β-rays	γ-rays
Nature	Helium Nucleus	Electron/Positron	Electromagnetic Radiation
Charge	+2e	±e	0
Mass	4 u	Very Small	0
Penetrating Power	Least	Moderate	Highest
Ionizing Power	Highest	Moderate	Lowest

Important Definitions

Radioactivity

The spontaneous disintegration of an unstable atomic nucleus accompanied by the emission of α, β, or γ radiations is called radioactivity.

Radioactive Decay

The process by which an unstable nucleus emits radiations and transforms into a more stable nucleus is called radioactive decay.

Alpha Particle

An alpha particle is a helium nucleus consisting of two protons and two neutrons.

Beta Particle

A beta particle is a fast-moving electron or positron emitted from the nucleus during radioactive decay.

Gamma Ray

Gamma rays are high-energy electromagnetic radiations emitted from an excited nucleus.

Frequently Asked Questions (FAQs) : 

1. Who discovered radioactivity?

Radioactivity was discovered by A. H. Becquerel in 1896.

2. What is radioactivity?

Radioactivity is the spontaneous emission of radiation from an unstable atomic nucleus.

3. Why is radioactivity called a nuclear phenomenon?

Because the emission of radiation originates from the nucleus of an atom.

4. What are the three types of radioactive decay?

The three types are Alpha (α), Beta (β), and Gamma (γ) decay.

5. Which radiation has the highest penetrating power?

Gamma rays (γ-rays) have the highest penetrating power.

6. Which radiation has the highest ionizing power?

Alpha particles (α-particles) have the highest ionizing power.

7. Are gamma rays charged particles?

No, gamma rays are neutral electromagnetic radiations and carry no charge.

8. Does temperature affect radioactivity?

No, radioactivity is independent of temperature, pressure, and chemical reactions.

9. What is an alpha particle?

An alpha particle is a helium nucleus represented as ⁴₂He.

10. What is radioactive decay?

Radioactive decay is the spontaneous transformation of an unstable nucleus into a more stable nucleus with the emission of radiation.