[7]This decay process proceeds in a series of steps, during which 6 alpha particles and 4 beta particles are emitted. (See [Appendix].)
[8]Named after their creator, John Napier, a Scottish mathematician (1550-1617), who also invented the decimal point.
[9]It is difficult to determine the half-life of ¹⁴C exactly. In the early days of ¹⁴C dating, in order not to delay continued work, an arbitrary value of 5568 years was chosen and this value is still used in calculations.
[10]This means that uranium decays through successive steps in which the entire series emits eight alpha particles. (See [Appendix].)
[11]Remember, this enormous period of time is a measure of the rate of spontaneous fission, not of the age of ²³⁸U.
[12]The rhenium-osmium scheme is shown below the dotted line because the method is still in an early experimental stage and its general utility is not yet established.
[13]For more on this family of elements, see Rare Earths, The Fraternal Fifteen, a companion booklet in this series.
[14]For a fuller explanation of the fission process, see Our Atomic World, another booklet in this series.
[15]Neutrons that have had their speed reduced by passing through a moderator (graphite, for example) which is built into every reactor to accomplish this very thing. For more about how this is done, see Nuclear Reactors and Research Reactors, companion booklets in this series.
[16]Note that some radionuclides sometimes decay by one method, sometimes by another. For example, 98.8% of the nuclei of actinium-227 emit a beta particle to form thorium-227; the remaining 1.2% emit an alpha particle to form francium-223; both of these daughter products decay to radium-223.