#### Answer

The mass number of an isotope is the sum of its protons and neutrons.

#### Work Step by Step

Every isotope of a substance will have a different mass number but the same atomic number.

Published by
Pearson

ISBN 10:
032191029X

ISBN 13:
978-0-32191-029-5

The mass number of an isotope is the sum of its protons and neutrons.

Every isotope of a substance will have a different mass number but the same atomic number.

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