Different radioactive elements have different half-lives. Why are the half-lives different for different elements? How is the half-life of a particular element measured?
In: Chemistry
I’ll start by explaining that the nucleus is a tiny ball containing protons and neutrons; there’s forces that want to hold them together, and other forces that want to tear them apart, and that depends a lot on the nucleus’s size. There’s a very narrow window of nucleus size for stable atoms, and if you have too many or too few neutrons, the nucleus will want to split. That’s why two isotopes (nuclei of the same element with different numbers of neutrons) will have different half-lives. When that split happens, it typically releases energy in the form of radiation, and becomes one or more smaller atoms of different elements.
The rate at which that split happens is measured in half-lives, or the time it would take for a given sample to have half of its atoms decay into different elements. So say you’ve got 1000 atoms of Carbon14. Under normal circumstances, it would take 5,730 years for 500 of those to decay. The half-life is 5,730 years.
Some isotopes like xenon-124 are technically radioactive, but their half-life is 10^22 years. It’s quite stable. That can be measured by having a large quantity and counting the number of atoms that decay using fancy instruments that can pick up radioactive decay. Others only exist for fractions of a second in particle colliders. Those are measured similarly, by estimating what you’re putting in and what you’re getting out in terms of radiation and end isotopes.
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