mass number
Plural
mass numbers
1
the total number of protons and neutrons in the nucleus of an atom
- The mass number of carbon-12 is 12, as it has 6 protons and 6 neutrons.
- Uranium-238 has a mass number of 238, indicating it has 92 protons and 146 neutrons.
- Helium-4 has a mass number of 4, comprising 2 protons and 2 neutrons in its nucleus.
- The mass number of oxygen-16 is 16, with 8 protons and 8 neutrons.
- When determining the mass number of an isotope, add the number of protons and neutrons together.
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