Beta-plus decay (or positron emission) is a type of radioactive decay in which a proton inside an unstable nucleus is transformed into a neutron, accompanied by the emission of a positron (the antimatter counterpart of the electron) and a neutrino.
Key Features:
- The atomic number decreases by one, as a proton becomes a neutron.
- The mass number remains unchanged, since the total number of nucleons is the same.
- The atom changes into a different element, one place earlier in the periodic table.
Why It Happens:
- Beta-plus decay occurs in nuclei with too many protons relative to neutrons.
- By converting a proton into a neutron, the nucleus moves toward a more stable proton-to-neutron ratio.
Role of the Positron and Neutrino:
- The positron is a positively charged electron that is quickly annihilated when it encounters an electron, releasing gamma rays.
- The neutrino carries away energy and momentum but interacts very weakly with matter.
Example:
An example is the decay of carbon-11 into boron-11, a process used in positron emission tomography (PET) in medical imaging.
In summary, beta-plus decay transforms a proton into a neutron and emits a positron and neutrino, altering the element and helping the nucleus reach a more balanced state.