Nuclear reaction: ¹⁸F → ¹⁸O + e⁺(positron) + ve(electron neutrino).
Beta decay is radioactive decay in which a beta ray and a neutrino are emitted from an atomic nucleus.
There are two types of beta decay: beta minus and beta plus.
In beta plus decay, a proton is converted to a neutron, positron and an electron neutrino, so mass number does not change. In this nuclear reaction, fluorine (atomic number 9) changes to oxygen (atomic number 8), because fluorine lost one proton.
In beta minus decay, neutron is converted to a proton and an electron and an electron antineutrino.