Radiocarbon dating and the old wood problem
It can capture an electron or it can emit a positron.Electron emission therefore leads to an increase in the atomic number of the nucleus.Neutron-poor nuclides with atomic numbers less than 83 tend to decay by either electron capture or positron emission.Many of these nuclides decay by both routes, but positron emission is more often observed in the lighter nuclides, such as A third mode of decay is observed in neutron-poor nuclides that have atomic numbers larger than 83.The product of this reaction can be predicted, once again, by assuming that mass and charge are conserved. They rapidly lose their kinetic energy as they pass through matter.As soon as they come to rest, they combine with an electron to form two -ray photons in a matter-antimatter annihilation reaction.-decay are often obtained in an excited state.The reaction is usually accompanied by the ejection of one or more neutrons.
Nuclei can also decay by capturing one of the electrons that surround the nucleus.
A more useful quantity is obtained by dividing the binding energy for a nuclide by the total number of protons and neutrons it contains.
This quantity is known as the binding energy per nucleon.
The excess energy associated with this excited state is released when the nucleus emits a photon in the -ray portion of the electromagnetic spectrum.
Most of the time, the -ray is emitted within 10Nuclides with atomic numbers of 90 or more undergo a form of radioactive decay known as spontaneous fission in which the parent nucleus splits into a pair of smaller nuclei.
Electron capture leads to a decrease of one in the charge on the nucleus.