Radioactive Decay and Half-Life Simulator

You're studying nuclear chemistry and the textbook says carbon-14 has a half-life of 5,730 years. You understand that means half of any sample decays in that time. But what does the curve actually look like? After three half-lives, how much is left? What if you started with 100 grams of iodine-131 instead?

Watch the curve

The half-life simulator lets you pick from a library of real isotopes — carbon-14, uranium-238, iodine-131, cobalt-60, and others. Set your initial mass, and the tool draws the exponential decay curve as an SVG chart. You can see the mass remaining at any time point, plus the fraction remaining, the number of half-lives elapsed, and the approximate activity in becquerels.

The visual makes the math intuitive. After one half-life, you're at 50%. After two, 25%. After three, 12.5%. The curve drops steeply at first and then flattens out, which is why radioactive materials are dangerous early on but eventually become negligible. Seeing the shape of the curve is more memorable than reading the formula N(t) = N₀ × (1/2)^(t/t½).

Real-world applications

Medical isotopes like iodine-131 (half-life about 8 days) are used in thyroid treatments. Doctors need to know how much radioactivity remains in a patient after a certain number of days. The simulator lets you play with those numbers directly.

Carbon-14 dating is another classic application. If an archaeological sample has 25% of the original carbon-14, that's two half-lives, which means about 11,460 years. You can verify that on the half-life simulator by setting the mass and scrubbing the time slider.

For looking up the properties of the parent atom, the periodic table is right there. Between the two tools you can go from element properties to decay curves without leaving the site.