Radioactive carbon dating rocks
A more useful quantity is obtained by dividing the binding energy for a nuclide by the total number of protons and neutrons it contains.
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 mass defect of an atom reflects the stability of the nucleus.
It is equal to the energy released when the nucleus is formed from its protons and neutrons.
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.