Combined Science GCSE
Mass number
What Mass number means in Combined Science GCSE, as defined for AQA.
Definitions of Mass number
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Reference: AQA
The number written as a superscript before the element symbol, counting protons plus neutrons in the nucleus.
Equals the number of protons plus the number of neutrons, so it distinguishes isotopes of the same element.
The sum of the protons and neutrons in an atom, a whole-number count of nucleons with no unit.
Equals protons plus neutrons, so neutrons are found by subtracting the atomic number from it.
This equals the number of protons plus the number of neutrons, so it reflects nuclear mass.
The sum of the protons and neutrons in an atom, ignoring the electron contribution.
Topics that use Mass number
- Mass number, atomic number and isotopes (AQA GCSE)
- Size and mass of atoms (AQA GCSE)
Related terms
- Atomic number
- Isotopes
- Nuclide notation
- Relative atomic mass
- Atomic structure
- Electron arrangement and outer electrons
- Empty space
- Ion formation
Using Mass number in the exam
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