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I think this question is common, but i want a little help. I'm little confused. What I concluded.
Relative atomic mass/Atomic weight (both are exactly the same) - It is the mass of atom calculated as taking the sum of all the masses of the subatomic particles and dividing it with mass of (the same technique calculated) 1/12th of C-12 atom.
Atomic mass- It is the mass of the atom calculated as taking the mean according to their abundances in nature, of atomic weight of the different isotopes present in that sample.
Mass Number- It is the mass calculated as the sum of the nucleons , as there is only a slight difference in the mass of the proton and neutron, and the mass of electron is negligible as compared with the mass of the proton and neutron
But this is conflicting with definitions on wikipedia. Also the relative atomic of carbon should be exactly 12, but its 12.011