- The existence of two or more chemical compounds with the same molecular
formula but having different properties owing to a different arrangement
of atoms within the molecule.
E.g., ammonium cyanate, NH4CNO, and urea,
CO(NH2)2, are isomers.
See also tautomerism.
- In nuclear physics, nuclei having
the same atomic number, but which exist
in different energy states are said to be isomeric. E.g., a nucleus
in its ground state and a nucleus
in a metastable excited state
are isomers. Nuclear isomers are formed by bombardment or in a radioactive
decay chain. They usually have very short half-lives
and decay by emitting gamma rays.
AND NUCLEAR PHYSICS