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Topic: Atomic Mass

How determined atomic mass of every element
which has many isotopes...?

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Re: Atomic Mass

Atomic mass is a sum total of mass of protons and mass of neutrons present in the nucleus of the atom. The mass of one proton is = 1 Dalton = 1 amu (atomic mass unit).
wt of electron = 0.0055 amu

As mass of electron is negligible, it is not considered for determination of atomic mass.

e.g. Na atom has 11 protons and 12 neutron in its nucleus
therefore, atomic mass (A)=11+12=23

No. of protons in nucleus is called atomic number (z).
usually,  no. of protons and that of neutrons remains same in an atom.

An elements having same atomic number but different atomic mass are called isotopes.

e.g. C12 and C14.
both have Z=6 but A=12 and 14