Question

atomic number and mass number.

Answer 1

Mass number is the number of protons and neutrons in an atom, and it tells us about the mass of the atom in amu, oratomic mass units. Atomic mass is the average mass of all the isotopes of a certain type. It is a weighted average that takes into account the abundances of all of the different isotopes.
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Answer 2

Atomic no. Is the no. Of protons present in nucleus, whereas
Mass no. Is the sum of no. Of protons and neutrons in the nucleus
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