Example concept half life used radiometric dating
A curie of activity, for example, represents 37 billion atoms decaying every second (37 billion dps) – a very large number!– while one (1) becquerel is equivalent to a single atom decaying each second.After two (2) half-lives, one-fourth of the initial activity, or 0.5 curies, would be left.After three (3) half-lives, which is more than 17,000 years later, one-eighth of the original C-14 activity, or 0.25 curies, would remain, and so forth. Each radionuclide has its own characteristic half-life.A decay, also known as a disintegration of a radioactive nuclide, entails a change from an unstable combination of neutrons and protons in the nucleus to a stable (or more stable) combination. Radioactive atoms decay principally by alpha decay, negative beta emission, positron emission, and electron capture.The type of decay determines whether the ratio of neutrons to protons will increase or decrease to reach a more stable configuration. How does the neutron-to-proton number change for each of these decay types?Since the half-life is defined for the time at which 50% of the atoms have decayed, why can’t we predict when a particular atom of that element will decay?
A half-life is defined as the amount of time required for one-half or 50% of the radioactive atoms to undergo a radioactive decay.
In a similar way, we know that, when dealing with a lot of radioactive atoms, we can accurately predict when one-half of them have decayed, even if we do not know the exact time that a particular atom will do so.