Uranium 238 (U-238) has a half-life of almost 4.5 billion years, which makes it the longest-lived uranium isotope. But thorium 232 has a half-life of over 14 billion years, which is much longer.
Also asked, what does half life mean when referring to radioisotopes?
Not all of the atoms of a radioisotope decay at the same time, but they decay at a rate that is characteristic to the isotope. The rate of decay is a fixed rate called a half-life. The half-life of a radioisotope describes how long it takes for half of the atoms in a given mass to decay.
How do you calculate the half life of a radioisotope?
A radioactive half-life refers to the amount of time it takes for half of the original isotope to decay. For example, if the half-life of a 50.0 gram sample is 3 years, then in 3 years only 25 grams would remain. During the next 3 years, 12.5 grams would remain and so on.
Which radioactive isotopes has the shortest half life?
You may wonder which naturally-occurring element has the shortest half-life. That would be francium, element 87, whose longest-lived isotope, francium-223, has a half-life of 22 minutes, decaying either into radium by beta decay or astatine by alpha emission.