Although it is not obvious at first, -decay increases the ratio of neutrons to protons.
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 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.
The solid line represents a neutron to proton ratio of 1:1.
Neutron-poor nuclides decay by modes that convert a proton into a neutron.