Alpha Decay Experiment for Schools, Teachers, and Students
Alpha decay is a type of radioactive decay in which an unstable atomic nucleus emits an alpha particle (α), consisting of two protons and two neutrons. This results in the formation of a new nucleus with reduced mass and atomic numbers.
Alpha Particle
An alpha particle is a helium nucleus (⁴₂He):
α = ⁴₂He
It consists of:
- 2 protons
- 2 neutrons
- Charge: +2e
- Mass: 4 amu (6.64 × 10⁻²⁷ kg)
Alpha Decay Process
When a nucleus undergoes alpha decay, it emits an alpha particle, resulting in:
- A decrease in mass number (A) by 4
- A decrease in atomic number (Z) by 2
The general reaction is:
A_Z X → A-4_{Z-2} Y + ⁴₂He + Energy
Where:
- A_Z X: Parent nucleus
- A-4_{Z-2} Y: Daughter nucleus
- ⁴₂He: Alpha particle
Example: Alpha Decay of Uranium-238
²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He + Energy
Here:
- Parent nucleus: Uranium-238
- Daughter nucleus: Thorium-234
- Emitted particle: ⁴₂He (alpha particle)
Energy Released in Alpha Decay
The energy released (Q) in alpha decay is given by:
Q = (m_parent – m_daughter – m_α) c²
Where:
- m_parent: Mass of the parent nucleus
- m_daughter: Mass of the daughter nucleus
- m_α: Mass of the alpha particle
- c: Speed of light (3 × 10⁸ m/s)
Key Features of Alpha Decay
- It occurs in heavy nuclei (Z > 82) like uranium, radium, and polonium.
- The emitted alpha particle has high energy but low penetration power due to its large mass and charge.
- Alpha particles can be stopped by a sheet of paper or human skin.
- The decay decreases the stability of the parent nucleus, leading to a more stable daughter nucleus.
Applications of Alpha Decay
- Smoke Detectors: Americium-241 (²⁴¹₉₅Am) undergoes alpha decay to detect smoke particles.
- Cancer Treatment: Alpha particles are used in targeted radiation therapies.
- Nuclear Energy: Provides insights into radioactive decay and nuclear reactions.
Observations
- Alpha decay reduces the atomic number by 2 and the mass number by 4.
- The emitted alpha particles are positively charged and interact strongly with matter.
- The decay process is governed by quantum tunneling, where the alpha particle escapes through the nuclear potential barrier.
Alpha decay is a fundamental process of nuclear disintegration in heavy nuclei, playing a significant role in nuclear physics and practical applications. It highlights the interplay of nuclear forces and quantum mechanics.
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