After one half-life has elapsed, one half of the atoms of the substance in question will have decayed.
Many radioactive substances decay from one nuclide into a final, stable decay product (or "daughter") through a series of steps known as a decay chain.
Various methods exist differing in accuracy, cost and applicable time scale.
All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.
This analysis provides a radiocarbon age of the sample, which must then be calibrated in accordance with a radiocarbon dating calibration curve such as the one pictured below.
A variety of factors have caused the amount of 14C present in the atmosphere to vary over time, resulting in deviations between the age predicted by radiocarbon dating and the absolute date of a specimen. Sample contamination must be carefully avoided to ensure measurement accuracy. Cornell University Press, Itha “Dating In Exposed and Surface Contexts”, ed.: Beck, Charlotte. Seminar Press, New York: NY, 1973 “Radiocarbon Dating”.
In the 1930s, he was a chemistry instructor at Berkeley and a researcher with an ambitious group of radiochemists at the university’s Lawrence Radiation Laboratory. And the discoveries made during that time are still the main bulwark and substance of chemical nuclear chemistry,” Libby later recalled.