Definition of mass number in English:

mass number

Line breaks: mass num¦ber


  • The total number of protons and neutrons in a nucleus.
    More example sentences
    • The sum of the protons and neutrons is called the mass number.
    • 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.
    • The mass number gives you the total number of protons and neutrons in the nucleus of that element.

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