The "Mass Excess" of a nuclide is the difference between its actual mass and its mass number in atomic mass units. It is one of the predominant methods for tabulating nuclear mass.
Applicable units are those of quantitykind:Mass
http://en.wikipedia.org/wiki/Mass_excess
The "Mass Excess" of a nuclide is the difference between its actual mass and its mass number in atomic mass units. It is one of the predominant methods for tabulating nuclear mass.
$\Delta = m_a - Am_u$, where $m_a$ is the rest mass of the atom, $A$ is its nucleon number, and $m_u$ is the unified atomic mass constant.
http://www.iso.org/iso/catalogue_detail?csnumber=31895