Question

How does elemt's atomic mass differ from its mass number?

Answer 1

The mass number is the sum of the number of protons and neutrons in an atom. It is a whole number. The atomic mass is the average number of protons and neutrons for all natural isotopes of an element.

Answer 2

Mass number is a whole number because it is the sum of number of proton and number of neutrons whereas atomic mass is fractional because it is the average relative mass of its atoms as compared with mass an atom of C-12 isotope taken as 12.

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