isotopi

Isotopi, or isotopes, are variants of the same chemical element that share the same atomic number but differ in the number of neutrons, resulting in different mass numbers. Because they have the same electron configuration, they largely behave the same chemically, but their physical properties can differ. Some isotopes are stable, while others are radioactive and decay over characteristic timescales.

Elements can have multiple isotopes with a range of stability. The existence of stable isotopes is common, but some elements have no stable isotopes at all (for example, technetium and promethium). The notation for isotopes commonly uses a mass number prefix, such as 12C, 13C, or 14C, with A representing the total mass number and Z the atomic number in more formal nuclear notation.

Natural abundance varies by element. Each element has a characteristic mix of isotopes in nature; for instance, carbon is mostly 12C with about 1% 13C, while oxygen shows a measurable ratio of 18O to 16O. Radioactive isotopes decay at rates described by their half-lives, and their abundances change over time.

Applications of isotopes are extensive. Radiometric dating uses isotopes such as carbon-14 to estimate ages of organic materials; medical uses include diagnostic and therapeutic isotopes (for example, technetium-99m and iodine-131). Stable isotopes serve as tracers in chemistry and biology, and isotope ratio measurements provide clues in geology, climatology, and environmental science.

Because isotopes have nearly identical chemical properties, they are not separated by typical chemical methods; instead, physical techniques such as mass spectrometry or centrifugation exploit mass differences to distinguish them.