The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
atoms that differ from most atoms of a given element in terms of radioactivity or isotopic mass. The tracer technique makes it possible to follow the motion of atoms of an element or its compounds in various processes.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.