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What is Mass number in Biology? PDF | Download eBooks

Learn Mass number definition in biology with explanation to study “What is Mass number”. Study mass number explanation with biology terms to review biology course for online degree programs.

Mass number Definition

  • Mass number is the sum of protons plus neutrons in the nucleus of an atom.

    Campbell Biology by J.B. Reece, L.A. Urry, M.L. Cain, S.A. Wasserman, P.V. Minorsky, R.B. Jackson



Mass number Explanation

The mass number is also called atomic mass number or nucleon number and is the total number of protons and neutrons in an atomic nucleus. It determines the atomic mass of atoms. The mass number however may be different for each isotope of an element. For example, the most common isotope of carbon is carbon-12 and has 6 protons and 6 neutrons. This is not the same as the atomic number (Z) which denotes the number of protons in a nucleus, and thus uniquely identifies an element. Hence, the difference between the mass number and the atomic number gives the number of neutrons (N) in a given nucleus by N=A-Z.

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