mass number
(mass-num-ber)
3 syllables
Definition
noun. the total number of protons and neutrons in the nucleus of an atom, which determines the atomic mass of an element.
Example Sentence
The mass number of an atom is essential for understanding its isotopes.
More Example Sentences
In chemistry class, we learned how to calculate the mass number from the periodic table.
Synonyms
nuclear mass; atomic mass; nucleon number
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mass number
