Radioactive decay and half-life calculator

Choose an isotope and move through time to see how many nuclei remain, with the decay curve, the decay constant and a sample of atoms decaying at random.

Learn radioactivity properly

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Questions students ask

What is half-life?

The time for half of the radioactive nuclei in a sample to decay.

How much is left after three half-lives?

One eighth: half of a half of a half, 12.5%.

Free notes on radioactivity

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