Question

which atomic scale is used nowadays by scientists to compare the masses of different atoms or elements

Answer 1

Using a mass spectrometer, physicists have determined the mass of a hydrogen atom to be 1.660538921(73) × 10-27kilograms, where the parenthetical digits are not known with complete certainty. That's accurate enough for most purposes.
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Answer 2

Answer:

Atomic weight, also called relative atomic mass, ratio of the average mass of a chemical element's atoms to some standard. Since 1961 the standard unit of atomic mass has been one-twelfth the mass of an atom of the isotope carbon-12.

Explanation:

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