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 has to do with figuring out the age of ancient things.If you could watch a single atom of a radioactive isotope, U-238, for example, you wouldn’t be able to predict when that particular atom might decay.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.Radioactive dating is helpful for figuring out the age of ancient things.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.