What causes beta plus decay?
β⁺ decay occurs because a nucleus has too low a neutron:proton ratio to be stable.
β⁺ decay is a process in which a nucleus emits a positron. A positron is the antimatter counterpart of an electron.
The nuclear symbol for a β⁺ particle is
Most nuclei are unstable if the neutron-proton ratio is less than 1:1 (for small nuclei) or 1.5:1 (for larger nuclei). That is, there are too many protons.
One way for the nucleus to become more stable is by β⁺ decay. This increases the number of neutrons and decreases the number of protons.
Magnesium-23 has 12 protons and 11 neutrons. The neutron:proton ratio is 11:12 or 0.92:1. It undergoes β⁺ emission to form sodium-23.
Sodium-23 has 12 neutrons and 11 protons. The neutron:proton ratio is 12:11 = 1.09:1, so sodium-23 has a stable nucleus.