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GCSE Physics · key term
The total number of protons and neutrons in a nucleus.
Used by AQA, Edexcel and OCR
Specification 4.4.1.2, 4.4.2.2 · Paper 1
The total number of protons and neutrons in an atomic nucleus.
Revise: Mass number, atomic number and isotopesThe notation therefore communicates the element's identity, the particular nuclear mass number and, when present, its electrical charge.
The total number of protons and neutrons in a nucleus, written at the upper left of a nuclide symbol.
Specification 6.4, 6.18, 6.19, 6.22, 6.38P · Paper 1
The total number of protons and neutrons in an atomic nucleus.
Revise: Nucleus CharacteristicsThe additional neutron makes carbon-13 the more massive isotope and raises its mass number from 12 to 13.
The total number of protons and neutrons in a nucleus, written at the upper left of a nuclide symbol.
Specification P6.1b, P6.1c, P6.1e, P6.1f, P6.1g · Paper 2 (Foundation), Paper 4 (Higher)
The total number of protons and neutrons in an atom's nucleus.
Revise: Isotopes and massThe isotope names record this difference in mass number.
The total number of protons and neutrons in a nucleus; it is the upper number, , in a nuclear symbol.
A number equal to the total number of protons and neutrons in a nucleus, written at the upper left of a nuclide symbol.
Paper 1, Paper 2
The total number of protons and neutrons in a nucleus, represented by .
Revise: Isotopes and Radioactive EmissionsIsotopes are nuclei of the same element with the same proton number but different neutron numbers. They consequently have different mass numbers.
Use the atomic number, not the mass number, to identify an element.
Calculate neutrons using mass number minus atomic number. Do not include electrons in the mass number.
For alpha decay, do not confuse the two changes: the mass number decreases by 4, while the atomic number decreases by 2.
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