How to solve radioactive dating problems
Half of what remains decay in the next half-life, and half of those in the next, and so on.This is an exponential decay, as seen in the graph of the number of nuclei present as a function of time.
If an individual nucleus makes it through that time, it still has a 50% chance of surviving through another half-life.
Even if it happens to make it through hundreds of half-lives, it still has a 50% chance of surviving through one more.
The probability of decay is the same no matter when you start counting. The chance of heads is 50%, no matter what has happened before.
The concept of half-life is applicable to other subatomic particles, as will be discussed in Particle Physics.
It is also applicable to the decay of excited states in atoms and nuclei.