isotoopeja

Isotoopeja, or isotopes, are variants of the same chemical element that have the same number of protons but different numbers of neutrons. This changes the mass of the nucleus and its stability, while the chemical behavior remains largely the same. Isotopes of an element share the same position on the periodic table and are usually written with the element symbol and a mass number, such as carbon-12 or uranium-235.

Isotopes can be stable or radioactive. Stable isotopes do not decay, while radioactive isotopes (radioisotopes) decay with characteristic half-lives. The neutron-to-proton ratio largely determines stability. The mass number A equals Z plus N, and isotopes of the same element can have different physical properties, such as density or nuclear reaction rates, even though their chemistry is similar.

Common examples include hydrogen’s protium (1H), deuterium (2H), and tritium (3H); carbon-12 and carbon-13 (stable), and carbon-14 (radioactive); uranium-235 and uranium-238 (both natural, with 235U being fissile). Some elements have no stable isotopes.

Natural isotopes occur in varying abundances; many elements have multiple stable isotopes. Radioisotopes are produced naturally in the environment and synthetically in reactors or particle accelerators. Applications include radiocarbon dating (14C), medical imaging and therapy (e.g., 18F, 131I), industrial tracing, and fundamental research.

Notation uses X-A or X with superscript A to indicate the mass number. Isotopic composition is measured by methods such as mass spectrometry. Safety and regulation govern the production, handling, and disposal of radioactive isotopes.