binding energy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The net energy needed to decompose a molecule, atom, or nucleus into its components.
• noun The net energy needed to remove an atomic electron to an infinitely remote position from its orbit.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics The energy needed to separate the constituent parts of an atom or nucleus; equivalent to the mass defect.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the energy required to separate particles from a molecule or atom or nucleus; equals the mass defect