Stereoisomerism

Part of speech: noun

Pronunciation: /ˌstɛɹɪəʊaɪˈsɒməɹɪzəm/

Definitions

1. The phenomenon of exhibiting the same molecular formula and connectivity of atoms while differing in the spatial arrangement of those atoms is a key feature of certain molecules
2. A type of isomerism where compounds share identical molecular formulas but differ in the orientation of their atoms in three-dimensional space
3. This occurrence involves variations in the structural alignment of atoms in molecules, leading to different chemical and physical properties despite a common formula

Etymology: Stereoisomerism is a compound built from two older pieces: "stereo-", from the Ancient Greek "stereos", meaning solid or three-dimensional, and "isomerism", the broader term for compounds that share a formula but differ in structure. Put together, the name describes a single idea: molecules with identical atoms, bonded in identical order, that differ only in how those atoms are arranged in space. The "isomer" half traces back to Greek "isos", meaning equal, and "meros", meaning part, so an isomer is a compound with "equal parts" in its formula but a different arrangement. The suffix "-ism" comes from Greek "-ismos", a common ending for nouns naming a condition or state. Chemists joined these elements in English to name a condition that could only be seen once they pictured molecules as three-dimensional objects.