posted by Mary .
Isotopes of the same element always have the same
Is the answer AMU number?
The AMU (Atomic mass unit) is a unit of mass. The AMU number is therefore the approximate total mass, which includes the number of neutrons, and thus can vary between isotopes.
The A-number represents the total number of neutrons and protons. Since the number of neutrons varies between isotopes, so does the A-number.
The Z-number is the number of protons, and does not vary between isotopes.
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