Here's a breakdown:
* Radioactive decay is a random process: There is no way to predict when a specific atom will decay. It's like flipping a coin, where each flip has a 50/50 chance of landing heads or tails.
* Half-life: This is the time it takes for half of the radioactive atoms in a sample to decay. It's a measure of the average decay rate, not a fixed point where half the atoms suddenly decay.
* Exponential decay: The number of radioactive atoms decreases exponentially over time. This means that after one half-life, half of the atoms remain, after two half-lives, a quarter remain, and so on.
Imagine a sample with 100 radioactive atoms:
* After one half-life, approximately 50 atoms will have decayed, leaving 50 undecayed.
* After two half-lives, approximately 25 atoms will remain.
* After three half-lives, approximately 12.5 atoms will remain.
Important note: While the half-life is a useful concept for describing the average decay rate, individual atoms don't "wait" for their turn to decay. Each atom has its own chance of decaying at any given moment.
In summary: It's not about half of the atoms decaying, it's about the probability of decay over time. The half-life helps us understand how quickly a sample will decay on average, but it doesn't dictate which atoms will decay when.
