There are three main types of radioactivity:
- Alpha Decay: In alpha decay, an atomic nucleus emits an alpha particle, which consists of two protons and two neutrons. This emission causes the original atom to decrease its atomic number by 2 and its mass number by 4. Alpha particles have a positive charge and are relatively large, so they don't penetrate matter very far and can be stopped by a sheet of paper or a few centimeters of air.
- Beta Decay: Beta decay involves the emission of either a beta-minus particle (an electron) or a beta-plus particle (a positron) by an unstable atomic nucleus. In beta-minus decay, a neutron in the nucleus transforms into a proton, and an electron and an antineutrino are emitted. In beta-plus decay, a proton in the nucleus transforms into a neutron, and a positron and a neutrino are emitted. Beta particles are smaller and more penetrating than alpha particles, but they can be stopped by a few millimeters of aluminum or a few meters of air.
- Gamma Decay: Gamma decay, or gamma radiation, is the emission of high-energy photons from an atomic nucleus. It often accompanies alpha or beta decay and serves to release excess energy from the nucleus. Gamma rays are electromagnetic waves and have no charge or mass. They are highly penetrating and can only be effectively shielded by dense materials such as lead or concrete.
It's important to note that these three types of radiation differ in their properties and ability to penetrate matter. They are collectively referred to as ionizing radiation because they can ionize atoms by removing or adding electrons, which can potentially damage living cells and genetic material.