Final answer:
The mass number represents the total number of protons and neutrons in the nucleus, while the atomic mass represents the weighted average mass of all the isotopes of an element.
Step-by-step explanation:
The mass number of an element is the total number of protons and neutrons in the nucleus of an atom. It is represented as 'A' in the element's symbol. For example, the mass number of carbon-12 is 12. On the other hand, the atomic mass of an element is the weighted average mass of all the isotopes of that element taking into account their natural abundance. It is represented as 'M' in the element's symbol. For example, the atomic mass of carbon-12 is 12.01.
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