Meaning & use
mass number
The total number of protons and neutrons in the nucleus of an atom.
See it in a sentence
Carbon-14 has a mass number of 14, reflecting its six protons and eight neutrons.
Students calculated the mass number of each isotope listed on the worksheet.
A note on using this word
Mass number is a whole number and should not be confused with atomic mass, which is an average that accounts for the relative abundance of different isotopes.
Words with a similar meaning
This term is best learned through its definition and examples.
Choose a synonym to suit the sentence. Meanings can overlap without being identical.
Make it your own
Write a sentence using “mass number”, then compare your use with the examples above.
Your draft stays on this page and is not sent anywhere.