Stable nuclei exist in the "band of stability" based on their neutron to proton ratio. Those with too many neutrons undergo beta decay to become more stable, while those with too many protons either capture electrons or emit positrons to become more stable. All nuclei above atomic number 83 are radioactive and undergo alpha decay. The half-life of a radioactive isotope is the time for half of it to decay, and varies greatly between isotopes. Nuclear transformations can occur naturally through radioactivity or artificially by bombarding nuclei with particles, allowing one element to be transformed into another.

1. 28.2 Nuclear Transformations

10. *Notice the shape of the graph