The Three Radiations
The Three Radiations
- An unstable nucleus loses energy by releasing radiation. There are three kinds: alpha, beta and gamma. They are very different from each other.
Alpha, beta and gamma
- An () is a helium nucleus: 2 protons and 2 neutrons. It is heavy and has charge .
- A () is a fast electron released from the nucleus, with charge . It is far lighter than an alpha-particle. There is also a positive form, the positron (), but the common one is the electron ().
- () is not a particle of matter. It is a burst of very high-frequency electromagnetic wave, like light but far more energetic. It has no mass and no charge.
Comparing the three
| Alpha (α) | Beta-minus (β⁻) | Gamma (γ) | |
|---|---|---|---|
| what it is | helium nucleus (2p, 2n) | fast electron | high-energy EM wave |
| charge | +2e | −e | 0 |
| relative mass | 4 | ≈ 1/2000 | 0 |
| speed | slow | fast | speed of light |
Your turn— tap to reveal the worked answer (9702/22/O/N/24 Q6(a))
Compare an alpha-particle with a beta-plus particle, in terms of their masses and their charges. (9702/22/O/N/24 Q6(a))
Answer: the alpha-particle has a much greater mass (4 against about 1/2000). Both are positive, but the alpha-particle has charge while the beta-plus has .