beepboard

erm, actually, unstable isotopes only go kaboom when they reach what is called their critical mass. To sustain a chain reaction of atoms kabooming causing other atoms kabooming, there needs to be enough energy from the kabooming atoms, as any less than that will mean that each atom's energy will on average cause less than one atom to kaboom, and the reaction "fizzles out". For most radioactive isotopes, it is very difficult to reach this critical mass, and for those that do, it is usually hard to separate them from other isotopes of the same element which are less radioactive since isotopes of the same element have nearly identical behavior.

On the contrary, kabooming can also happen as a result of chemical processes. For example, heating plutonium at high temperatures causes it to spontaneously combust. However, if you have an INCREDIBLY UNSTABLE ISOTOPE of plutonium instead of a mildly unstable isotope, it will decay into something like uranium, which I'm pretty sure doesn't burn at high temperatures the same way plutonium does (though it probably still burns, just not as readily). So, a more stable isotope of plutonium (e.g. plutonium-244) would actually kaboom more under this environment than a less stable one (e.g. plutonium-239).

Thus, in some cases, stable isotopes kaboom more than unstable ones.