isomerism

[ ahy-som-uh-riz-uhm ]

noun

1. Chemistry. the relation of two or more compounds, radicals, or ions that are composed of the same kinds and numbers of atoms but differ from each other in structural arrangement structural isomerism, as CH 3 OCH 3 and CH 3 CH 2 OH, or in the arrangement of their atoms in space and therefore in one or more properties. Compare optical isomerism, stereoisomerism.
2. Also called nu·cle·ar i·som·er·ism [noo, -klee-er ahy-, som, -, uh, -riz-, uh, m, nyoo, -]. Physics. the relation of two or more nuclides that have the same atomic number and mass number but different energy levels and half-lives.
3. Chemistry, Physics. the phenomenon characterized by such a relation.
4. the state or condition of being isomerous.

isomerism

/ aɪˈsɒməˌrɪzəm /

noun

1. the existence of two or more compounds having the same molecular formula but a different arrangement of atoms within the molecule See also stereoisomerism optical isomerism
2. the existence of two or more nuclides having the same atomic numbers and mass numbers but different energy states

Word History and Origins

Origin of isomerism¹

First recorded in 1830–40; isomer(ic) + -ism

Example Sentences

This kind of trans–cis isomerism happens often in biological systems, such as the chemical process underlying vision.

From Nature

What they discovered were new examples of nuclear isomerism, in which isotopes of identical mass numbers and changes show dramatically different radioactive characteristics.

From Literature

That example is the case of optical isomerism.

From Economist

From these results it follows that the two acids are structurally identical, and the isomerism has consequently to be explained on other grounds.

From Project Gutenberg

Cited2 deficiency results in heart defects in mice and in humans and can also lead to a serious type of heart defect called atrial isomerism, where the left-right asymmetry of the heart is disturbed.

From Reuters