Alpha Decay

Key Stage 5

Meaning

Alpha decay is a type of radioactive decay where an unstable nucleus emits an alpha particle consisting of two protons and two neutrons.

About Alpha Decay

• Reduces the Atomic Number atomic number by 2 and the mass number by 4.
• Common in heavy elements like uranium and radium.
• Alpha particles have low penetration depth but high ionizing power.
• Alpha decay is a form of spontaneous fission.
• The emitted alpha particle is a helium nucleus (He²⁺).
• Alpha decay results in a daughter nucleus that is more stable than the parent.
• The energy released during alpha decay is in the range of 4-9 MeV.
• Alpha decay can be detected using Geiger-Müller counters or scintillation detectors.

Examples

• Radium-226 decays to radon-222 by emitting an alpha particle.
• Smoke detectors often use americium-241, which undergoes alpha decay.