How do you know what element emits what type of radiation? Also how can you tell if an isotope is stable?

So how do you know whether an element undergoes alpha, beta or gamma decay? Can all elements decay undergo alpha, beta and gamma decay? Simply, how do you know what type of radiation is emitted?



How can you tell what type of isotope is stable or not? How can you identify them? Why are some isotpes stable while others are not?How do you know what element emits what type of radiation? Also how can you tell if an isotope is stable?
This has already been figured out by experiment and calculations. The best way now is just to look it up. See the first link for an active chart of all the elements, and the second link for an example of one element.



Every element has one or more radio-active isotopes.