The belt of stability makes it is easy to determine where the alpha decay, beta decay, and positron emission or electron capture occurs.
Decay: Alpha decay is located at the top of the plotted line, because the alpha decay decreases the mass number of the element to keep the isotope stable. This is accomplished by emitting a alpha particle, which is just a helium (He
) nucleus. In this decay pathway, the unstable isotope’s proton number P
is decreased by 2 and its neutron (N
) number is decreased by 2. The means that the nucleon number A
decreases by 4 (Equation 1).
Decay: Beta ??
decay accepts protons so it changes the amount of protons and neutrons. the number of protons increase by 1 and the neutron number decreases by 1. This pathway occurs in unstable nuclides that have too many neutrons lie above the band of stability (blue isotopes in Figure 1).
Decay: Positron ?+
emission and electron capture is when the isotope gains more neutrons. Positron emission and electron capture are below the band of stability because the ratio of the isotope has more protons than neutrons, think of it as there are too few protons for the amount of neutrons and that is why it is below the band of stability (yellow isotopes in Figure 1).
As with all decay pathways, if the daughter nuclides are not on the Belt, then subsequent decay pathways will occur until the daughter nuclei are on the Belt.