Radioactive Decay Types

Study Notes

Alpha Radiation:
- Composed of 2 protons and 2 neutrons (a helium nucleus).
- Emitted from an unstable atom's nucleus.
- Low penetrating power; stopped by paper or skin.
- Positive charge (+2).
- Slow speed.
- High ionizing power.
- Large mass (4 atomic mass units).
- Used in smoke detectors, radiotherapy, and tracer studies.
- Alpha decay is the emission of an alpha particle.
Beta Radiation:
- Composed of electrons (beta-minus: e⁻) or positrons (beta-plus).
- Emitted from the nucleus during neutron decay into a proton and an electron.
- Moderate penetrating power; stopped by aluminum or plastic.
- Negative charge (-1 for beta-minus), positive charge (+1 for beta-plus).
- Faster than alpha, but slower than gamma.
- Moderate ionizing power.
- Very small mass (nearly 0 atomic mass units).
- Used in thickness gauges, radiotherapy, and carbon dating.
- Beta decay is the conversion of a neutron to a proton and electron emission.
Gamma Radiation:
- High-energy electromagnetic radiation.
- Emitted from the nucleus, often after alpha or beta decay.
- Very high penetrating power; stopped by thick lead or concrete.
- No charge (neutral).
- Travels at the speed of light.
- Low ionizing power.
- Massless (photons).
- Used in sterilizing medical equipment, cancer treatment, and industrial radiography.
- Gamma decay releases energy without altering the number of protons or neutrons.

Feature	Alpha	Beta	Gamma
Composition	2p + 2n (He nucleus)	e⁻ (β⁻) or e⁺ (β⁺)	High-energy photon
Penetration	Low	Moderate	Very High
Charge	+2	-1 (β⁻), +1 (β⁺)	0
Speed	Slow	Fast (but not light)	Light speed
Ionizing Power	High	Moderate	Low
Mass	Large	Very small	None
Uses	Smoke detectors, radiotherapy	Thickness gauges, radiotherapy	Sterilization, radiotherapy