What are short-lived isotopes?

Answer 1

Short-lived isotopes are isotopes with relatively short half-lives. Note that short-lived is a relative term, and that means you need to make some kind of comparison to use the term correctly. Let's look at one example using cobalt, which has only one stable isotope, cobalt-59.

We make cobalt-60 by lowering a fixed amount of cobalt-59 into an operating nuclear reactor. It will bathe in the neutron flux there to become activated (neutron activation). The cobalt-59 absorbs a neutron and has been activated to become cobalt-60, which is an unstable isotope of cobalt. That means it is radioactive, and it has a half-life of 5.2714 years. If we look at another isotope, cobalt-58, we find it has a half life of 7.86 days. It's a short-lived isotope of cobalt, compared to cobalt-60. Need another example? Then let's do one more.

In the case of rubidium, the isotope rubidium-85 is the only stable isotope of this metal. Rubidium-87, on the other hand, has a half-life of 4.88x1010 years, which is longer than the estimated age of the universe. (Wow!) The isotopes rubidium-83 and rubidium-84 have half-lives of 86.2 days and 32.9 days, respectively. These two isotopes are short-lived isotopes of rubidium, at least compared to the long-lived rubidium-87 isotope.

There are many isotopes of elements that have been synthesized in the nuclear physics labs, and a lot of them have half-lives of less than one second. The term short-lived isotope is a relative term, and it should be used with that idea in mind. The difference between the two (or more) compared isotopes can be smaller, as in the case of cobalt, or larger, as we showed in rubidium. That difference doesn't have to be specific either, so remember that as well.

We'll depart with the idea that the term "short-lived isotope" is often encountered in medical imaging. The short-lived isotopes referred to usually have half-lives of days or even hours, and are synthesized shortly before use (because they don't last long).

Answer 2

Short-lived isotopes are radioactive isotopes that have a relatively short half-life, which is the time it takes for half of the radioactive atoms to decay. These isotopes decay rapidly and do not persist in the environment for a long time. They are often used in medical imaging, research, and various industrial applications.