Definition of mass number in English:

mass number

noun

Physics
  • The total number of protons and neutrons in a nucleus.

    • ‘Mathematical calculations employing the proportions and mass numbers have assigned titanium a mean atomic weight of 47.88.’
    • ‘The mass number gives you the total number of protons and neutrons in the nucleus of that element.’
    • ‘The sum of the protons and neutrons is called the mass number.’
    • ‘Different isotopes of the same element have different mass numbers because their nuclei contain different numbers of neutrons.’
    • ‘Various numbers are used to define nuclei: the atomic number, Z, is the number of protons, while the mass number is the sum of the atomic number and the number of neutrons, N.’

Pronunciation:

mass number

/ˈmas ˌnəmbər/