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atomic number vs. mass number

[uh-tom-ik nuhm-ber] / əˈtɒm ɪk ˈnʌm bər /

noun

  1. the number of positive charges or protons in the nucleus of an atom of a given element, and therefore also the number of electrons normally surrounding the nucleus. at. no.; Z

noun

Physics.
  1. the integer nearest in value to the atomic weight of an atom and equal to the number of nucleons in the nucleus of the atom. A