Mass Number (m): Difference between revisions

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== [[Orange Book]] Entry ==
== [[Orange Book]] Entry ==


The sum of the total number of protons and neutrons in an atom, ion or molecule.
The sum of the total number of protons and neutrons in an atom, ion or molecule.


== [[Gold Book]] Entry ==
== [[Gold Book]] Entry ==


Total number of heavy particles (protons and neutrons jointly called nucleons) in the atomic nucleus. Also called nucleon number. Symbol ''m'' in mass spectrometry.
Total number of heavy particles (protons and neutrons jointly called nucleons) in the atomic nucleus. Also called nucleon number. Symbol ''m'' in mass spectrometry.
== Proposed New Entry ==
Total number of nucleons (protons and neutrons) in an atom or molecule. Should be called nucleon number instead of mass number. Currently the symbol ''m'' is widely used in mass spectrometry. To avoid confusion between the nucleon number and mass, the symbol ''n'' should be used for the nucleon number.
The nucleon number ''n'' should not be used in mass spectra because:
# mass spectrometers measure mass/charge and not the number of nucleons nor the number of nucleons/charge
# the number of nucleons ''n'' is a natural number (whole number larger than zero) whereas mass spectrometers measure fractional masses.

Revision as of 18:22, 18 January 2005

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See proposed definition on the Mass Number (m) discussion page.


Orange Book Entry

The sum of the total number of protons and neutrons in an atom, ion or molecule.


Gold Book Entry

Total number of heavy particles (protons and neutrons jointly called nucleons) in the atomic nucleus. Also called nucleon number. Symbol m in mass spectrometry.