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mass number

mass number, often represented by the symbol A, the total number of nucleons (neutrons and protons) in the nucleus of an atom. All atoms of a chemical element have the same atomic number (number of protons in the nucleus) but may have different mass numbers (from having different numbers of neutrons in the nucleus). Atoms of an element with the same mass number make up an isotope of the element. Different isotopes of the same element cannot have the same mass number, but isotopes of different elements often do have the same mass number, e.g., carbon-14 (6 protons and 8 neutrons) and nitrogen-14 (7 protons and 7 neutrons).

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mass number

mass num·ber • n. Physics the total number of protons and neutrons in a nucleus.

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"mass number." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 18 Apr. 2018 <http://www.encyclopedia.com>.

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mass number

mass number (nucleon number) The total number of protons and neutrons found in the nucleus of an atom.

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"mass number." World Encyclopedia. . Encyclopedia.com. 18 Apr. 2018 <http://www.encyclopedia.com>.

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mass number

mass number The sum of the protons and neutrons in the nucleus of an atom.

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"mass number." A Dictionary of Earth Sciences. . Encyclopedia.com. 18 Apr. 2018 <http://www.encyclopedia.com>.

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