A radium-226 nucleus contains 88 protons and 138 neutrons. It decays by emitting an α\alphaα-particle and becomes a nucleus of an isotope of radon. The symbol for radium is Ra\text{Ra}Ra and the symbol for radon is Rn\text{Rn}Rn.
Write down the nuclide equation for this decay.
Cesium-137 is radioactive with a half-life of 30 years. A soil sample contaminated during an accident is analyzed. The quantity of cesium-137 in the sample is 12.5%12.5\%12.5% of the quantity present immediately after the accident.
Calculate the time that has elapsed since the accident occurred.
120 exam-style questions on CIE IGCSE Physics 5.2.3a Radioactive decay. Each one has a worked solution and a mark scheme showing where the marks go.