It soon became clear that the blackening of the plate had nothing to do with phosphorescence, as the blackening was also produced by non-phosphorescent salts of uranium and metallic uranium.
It became clear from these experiments that there was a form of invisible radiation that could pass through paper and was causing the plate to react as if exposed to light.
Another type of radioactive decay results in products that are not defined, but appear in a range of "pieces" of the original nucleus.
This decay, called spontaneous fission, happens when a large unstable nucleus spontaneously splits into two (and occasionally three) smaller daughter nuclei, and generally leads to the emission of gamma rays, neutrons, or other particles from those products.
Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula.
In some decays, the parent and the daughter nuclides are different chemical elements, and thus the decay process results in the creation of an atom of a different element. The first decay processes to be discovered were alpha decay, beta decay, and gamma decay.Alpha decay is one type of radioactive decay, in which an atomic nucleus emits an alpha particle, and thereby transforms (or "decays") into an atom with a mass number decreased by 4 and atomic number decreased by 2.Radioactive decay (also known as nuclear decay or radioactivity) is the process by which the nucleus of an unstable atom loses energy by emitting radiation, including alpha particles, beta particles, gamma rays, and conversion electrons.They are those that contain thirty-four radionuclides that date before the time of formation of the solar system, and are known as primordial nuclides.Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes such as potassium-40.