IB Physics E.3.2 Types of Radioactive Decay Key Definitions

Alpha decay occurs when an unstable nucleus emits an alpha particle, which is essentially a helium nucleus made up of two protons and two neutrons ($^4_2 \text{He}$).

In beta minus decay, a neutron in the nucleus is converted into a proton, emitting an electron ($\beta^-$) and an antineutrino ($\bar{\nu}$):

$$
n \rightarrow p + e^- + \bar{\nu}
$$

In beta plus decay, a proton is converted into a neutron, emitting a positron ($\beta^+$) and a neutrino($\nu$):

$$
p \rightarrow n + e^+ + \nu
$$

Gamma decay occurs when an excited nucleus releases excess energy by emitting a gamma ray, a high-energy photon.

An electrically neutral particle with negligible mass that interacts only weakly with matter. It is emitted in beta decay and carries away part of the energy and momentum released.