They need to be active long enough to treat the condition, but they should also have a short enough half-life so that they don’t injure healthy cells and organs.
Each parent nuclide spontaneously decays into a daughter nuclide (the decay product) via an α decay or a β decay.The final decay product, lead-208 (208Pb), is stable and can no longer undergo spontaneous radioactive decay.It then takes the same amount of time for half the remaining radioactive atoms to decay, and the same amount of time for half of those remaining radioactive atoms to decay, and so on. The amount of time it takes for one-half of a sample to decay is called the half-life of the isotope, and it’s given the symbol: It’s important to realize that the half-life decay of radioactive isotopes is not linear.For example, you can’t find the remaining amount of an isotope as 7.5 half-lives by finding the midpoint between 7 and 8 half-lives.The different methods of radiometric dating are accurate over different timescales, and they are useful for different materials.
After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a "daughter" nuclide, or decay product.
Understand how decay and half life work to enable radiometric dating.
Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object.
It might take a millisecond, or it might take a century. But if you have a large enough sample, a pattern begins to emerge.
It takes a certain amount of time for half the atoms in a sample to decay.
This half-life will be the rate-limiting factor in the ultimate transformation of the radioactive nuclide into its stable daughter(s).