1) Atom 2) Of an atomic form 
The word isotopic has a number of different meanings, including: ...
Of identical chemical composition but differing in some physical property, such as atomic weight. ... (05 Mar 2000) ... 
Type: Term Pronunciation: ī′sō-top′ik Definitions: 1. Of identical chemical composition but differing in some physical property, such as atomic weight.
Isotopic: Referring to an isotope, a form of a chemical element with the same atomic number as another element but having a different atomic mass. From the Greek 'iso-', equal, the same + 'topos', place. Isotopes are used in a number of medical tests.
[adj] - of or relating to or having the relation of an isotope
adjective of or relating to or having the relation of an isotope