Chemistry A-Level
mass number
What mass number means in Chemistry A-Level, as defined for AQA, OCR.
Definitions of mass number
Exam boards and our study guides word this term in slightly different ways. Learn the version your board uses.
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Reference: OCR
Gives the total of protons and neutrons, so neutrons equal the mass number minus the atomic number.
The total number of protons and neutrons, and it is always a whole number.
Topics that use mass number
- Mass number and isotopes (AQA A-Level)
- Atomic structure and isotopes (OCR A-Level)
Related terms
- atomic number
- isotopes
- relative isotopic mass
- abundance ratios
- acceleration to constant kinetic energy
- base peak
- Calculation accuracy
- carbon-13 satellite
Using mass number in the exam
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