Isomers

Part of speech: noun

Definitions

1. Forms of a compound that share the same chemical formula but have various arrangements of atoms or bonds affecting their properties
2. Chemical variants featuring the same molecular formula while exhibiting differences in structure or spatial orientation of atoms
3. Compounds possessing the same molecular formula but differing in the arrangement or connectivity of their atoms

Etymology: "Isomers" is the plural of "isomer", and the singular is built from two Greek elements: "isos", meaning "equal", and "meros", meaning "part". The combination is a modern scientific coinage rather than an ancient word, so the Greek parts describe the idea rather than a historical usage. Chemists needed a term for compounds whose molecules contain identical numbers of each kind of atom yet differ in structure. The "iso-" prefix is the same one found in words like "isobar" and "isotope", where it signals sameness of some kind, while "-mer" supplies the sense of a distinct portion or unit. Put together, an isomer is a compound whose "parts" are equal in count but arranged differently. The pairing of these two Greek roots reflects the chemistry precisely: the molecular makeup is the same, and only the arrangement changes.

Synonyms: variants, forms, types, structures, configurations