These nuclei undergo change spontaneously, that is, without outside help. When unstable nuclei undergo change they give off radiation. Atoms which have unstable nuclei are radioactive and are called ...

Key fact Half-life is the time it takes for the activity of the source to fall to half its original value. The illustration below shows how a radioactive sample is decaying over time. From the ...

Our planet is far older than people had thought! Students can understand the mechanism of radioactive half-life and how it helps determine age by experimenting with pennies, dice, and sugar cubes ...

For example, the half-life of Iodine 131 is eight days, but for Uranium 238, which is present in varying amounts all over the world, it is 4.5 billion years. Potassium 40, the main source of ...

The half-life of radioactive carbon-14 is 5,730 years. For example, if a sample of a tree (for example) contains 64 grams (g) of radioactive carbon, it will contain 32 g after 5,730 years and 16 g ...

Boltwood studied this concept of "radioactive series," and found that ... he knew the rate at which uranium breaks down (its half-life), he could use the proportion of lead in the uranium ores ...