All elements not found in the earth have been artificially produced. These radioactive elements have such short half-lives that they have vanished from the earth by decaying into other elements. An exception is plutonium. Scientists have found very small amounts of the plutonium isotope Pu-244 in the earth. Uses of radioisotopes.
Radioisotopes have many important uses in science and industry.
Because they are radioactive, they can be easily detected, even in very small amounts. They are identical chemically with other isotopes of the same element, so they can take the place of the common isotopes in chemical reactions. Thus, they can be used to study the details of chemical or biological reactions. For example, biochemists use radioactive carbon to trace the path of carbon atoms in the photosynthesis process in green plants. They detect the particles and rays emitted by the radioactive atoms with such devices as Geiger counters, gamma-ray spectrometers, and proportional counters.