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 ...

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 ...

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 ...

The radiation emitted from unstable nuclei is called ionising radiation because as it passes through matter it can dislodge outer electrons from atoms causing them to become ions. An unstable ...