Isotopes of tellurium
Naturally occurring tellurium on Earth consists of eight isotopes: 120, 122-126, 128, 130. The heaviest two have been found to be radioactive: 128Te and 130Te undergo double beta decay with half-lives of, respectively, 7.7×1024 years (the longest half-life of all nuclides proven to be radioactive) and 7.9×1020 years.