Noun
the sum of the number of neutrons and protons in an atomic nucleus
Source: WordNetA given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 u). Source: Internet
An example of a referral to a mass number is "magnesium-24," which is an atom with 24 nucleons (12 protons and 12 neutrons). Source: Internet
An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). Source: Internet
For example, the atomic mass of chlorine-35 to five significant digits is 34.969 u and that of chlorine-37 is 36.966 u. However, the atomic mass in u of each isotope is quite close to its simple mass number (always within 1%). Source: Internet
It has been suggested to have a transitory existence in nuclear reactions produced by helions that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. Source: Internet
However, no odd-even effect is observed on fragment mass number distribution. Source: Internet