Isotopy

Part of speech: noun

Definitions

1. A scientific concept referring to the occurrence of various isotopes of an element that share the same number of protons but differ in their neutron counts
2. A condition describing elements that possess isotopes characterized by equivalent atomic numbers yet different mass numbers, leading to unique behaviors
3. A phenomenon in which multiple isotopes of a chemical element exist, having the same atomic number but differing in neutron quantity, resulting in varied physical properties

Etymology: In 1913, the chemist Frederick Soddy needed a name for atoms of one element that had different atomic masses, such as the forms of lead produced by radioactive decay. A Scottish physician, Margaret Todd, suggested "isotope," from Greek "isos" (equal) and "topos" (place), because such atoms occupy the same place on the periodic table. Soddy adopted the coinage, and it became standard. He won the 1921 Nobel Prize in Chemistry, partly for this work on radioactive substances and isotopes. "Isotopy" is much rarer than "isotope" and is formed from it with the abstract suffix "-y," as in "geometry" or "allergy." In chemistry it is seldom used, so the noun is mostly found in its base form. A separate, unrelated sense exists in linguistics, where the French semiotician Algirdas Greimas used "isotopy" in the 1960s for a recurring semantic thread that holds a text together.