Radioactive Tracer
A radioisotope introduced into a system so that its pathway can be followed by detecting its radiation.
Unit
Bq
In depth
Because a radioisotope is chemically identical to the stable element, it follows exactly the same route while remaining detectable at vanishingly small quantities. Tracers reveal reaction mechanisms, metabolic pathways, and leaks in pipelines without disturbing the system.
Examples in the real world
Phosphorus-32 tracking fertiliser uptake in plants; oxygen-18 proving which bond breaks during esterification.