Alpha, beta, and gamma decay are three common ways unstable atomic nuclei become more stable.

Quick definitions

  • Alpha decay: the nucleus emits an alpha particle , which is 2 protons and 2 neutrons, so the atom’s atomic number goes down by 2 and its mass number goes down by 4.
  • Beta decay: a nucleus changes a neutron into a proton or a proton into a neutron, releasing a beta particle; this changes the element but keeps the mass number the same.
  • Gamma decay: the nucleus releases extra energy as a gamma ray without changing the number of protons or neutrons, so the element stays the same.

Main differences

Type| What is emitted| Changes element?| Mass number change| Penetration
---|---|---|---|---
Alpha| 2 protons + 2 neutrons| Yes| Decreases by 4| Low 17
Beta| Electron or positron| Yes| No change| Medium 17
Gamma| High-energy photon| No| No change| High 17

Simple way to remember

  • Alpha = heavy particle leaves.
  • Beta = one nuclear particle changes into another.
  • Gamma = energy leaves, but the nucleus stays the same element.

Example

If a nucleus loses an alpha particle, it becomes a different element with 2 fewer protons. If it undergoes beta decay, the element also changes, but the mass number does not. If it emits gamma radiation, it just drops to a lower ऊर्जा state and remains the same element.

If you want, I can also show these three decays with a one-line nuclear equation for each.