What is the difference between atomic mass and mass number?

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The atomic number of an atom is the number of protons in the nucleus of an atom. The number of electrons that orbit the nucleus is equal to the number of protons. The atomic number of an atom decides its chemical properties.

Atomic mass on the other hand is the...

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The atomic number of an atom is the number of protons in the nucleus of an atom. The number of electrons that orbit the nucleus is equal to the number of protons. The atomic number of an atom decides its chemical properties.

Atomic mass on the other hand is the total mass of an atom determined by adding the mass of the protons and neutrons in the nucleus as the mass of the electrons is negligible. Atoms with the same atomic number can have a different atomic mass if there is a difference in the number of neutrons in the nucleus, these are called isotopes.

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