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explain about atomic and molecular mass

The atomic mass (ma) is the mass of an atomic particle, sub-atomic particle, or molecule. It may be expressed in unified atomic mass units, which by International agreement is 1/12 mass of a single carbon-12 atom at rest.When expressed in such units, the atomic mass is called the relative isotopic mass (see section below).

The atomic mass of atomic particles is slightly less than the total mass of its constituting protons, neutrons, or electrons due to binding energy mass loss (as per E=mc2)

The molecular mass (ma) is the mass of a molecule.A number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom, which is taken to have a mass of 12.
Examples:
The molecular mass of C2H6 is approximately 30 or [(2 x 12) + (6 x 1)]. Therefore the molecule is about 2.5 times as heavy as the 12C atom or about the same mass as the NO atom with a molecular mass of 30 or (14+16)


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