The binding energy can also be viewed as the amount of energy it would take to rip the nucleus apart to form isolated neutrons and protons.It is therefore literally the energy that binds together the neutrons and protons in 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.Alpha decay is usually restricted to the heavier elements in the periodic table.(Only a handful of nuclides with atomic numbers less than 83 emit an -particle.) The product of -decay is easy to predict if we assume that both mass and charge are conserved in nuclear reactions.Alpha decay of the The sum of the mass numbers of the products (234 4) is equal to the mass number of the parent nuclide (238), and the sum of the charges on the products (90 2) is equal to the charge on the parent nuclide.
Consider what happens during the -decay of The difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons is called the mass defect.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 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.