Nominal mass

DRAFT DEFINITION
Nominal mass
The mass of an ion or molecule calculated using the mass of the most abundant isotope of each element rounded to the nearest integer value.
Considered between 2004 and 2006 but not included in the 2006 PAC submission
This is an unofficial draft definition presented for information and comment. Recommended terms | Full list of terms

See additional comments on the Nominal mass discussion page (archive of discussion between 2004 and 2006)

See proposed definition on the Nominal mass discussion page.

Related Terms

• Mass

External Links

• Base Peak Glossary

The mass of an ion containing the most abundant isotopes, calculated with nominal atomic weights.??????????????

• Little Encyclopedia of MS

The nominal mass of an ion is calculated by simply adding the integer masses of the lightest isotopes of all elements contributing to the molecule, e.g. to calculate the nominal mass of CH₃Br you have to use the nominal masses of ¹²C, ¹H, and ⁷⁹Br to obtain M_nomi = 94 amu

• Shimadzu Mass Spectrometry Glossary

Same meaning as mass number (Nearest integer when expressing the mass of an atom in units that define ¹²C as 12. The number is approximately the sum of protons and neutrons in the atomic nucleus. In mass analysis the mass number is the sum of the masses of the atoms making up an ion or other particle (¹²C = 12, ¹H = 1, ¹⁶O = 16, ¹⁴N = 14...))