You are perhaps not aware that all atoms are isotopes. An isotope is simply an atom with a specified number of neutrons. Some isotopes are radioactive, and those are probably the ones you are asking about. These are primarily used for medical purposes; radiation has a variety of uses, both diagnostic and therapeutic (radiation can be used to kill cancer cells, for example). There are also many other scientific activities that use radioactive isotopes, for example, the use of radioactive carbon to perform carbon dating, to find out how old something is (such as the Shroud of Turin, which as it turns out is not as old as it was claimed to be, although it is quite old).
This is important because each isotope has different properties.
The isotope 211At was proposed for the radiotherapy of cancers.
Isotopes in helium are not typically important because the most common isotope, helium-4, is stable and abundant. Helium-3, another isotope, is less common and has some specialized uses in scientific research and certain high-tech applications.
The most important isotope of promethium is Pm-147.
The isotopes are not manufactured for specific uses, they occur in nature naturally.
Iodine-131 (not iodone) is a radioactive isotope of iodine: this isotope has important applications in the treatment of thyroid diseases.
For the nuclear reactors and nuclear weapons the isotope plutonium-239 is important.
Isotopes are very important part of calculations in chemistry. They are different elements of same atomic number.
Deuterium oxide: 2H2O Uses deuterium, a heavier isotope of hydrogen.
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wee are all full of isotopes
The most important is carbon-12.