Dating with radioisotope
For example, of which 286 are primordial nuclides, meaning that they have existed since the Solar System's formation.
Soddy proposed that several types of atoms (differing in radioactive properties) could occupy the same place in the table.
Thomson channeled streams of neon ions through a magnetic and an electric field and measured their deflection by placing a photographic plate in their path.
The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact there are also 27 known radionuclides (see primordial nuclide) with half-lives longer than the age of the universe.
Adding in the radioactive nuclides that have been created artificially, there are 3,339 currently known nuclides.
The term isotopes (originally also isotopic elements).