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Date: 15-2-2018
2096
Date: 16-2-2018
1028
Date: 14-5-2020
996
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Relative atomic mass
Since the electrons are of minute mass, the mass of an atom essentially depends upon the number of protons and neutrons in the nucleus. As Table 1.1 shows, the mass of a single atom is a very small, non-integral number, and for convenience we adopt a system of relative atomic masses.
We define the atomic mass unit as 1/12th of the mass of a 126C atom so that it has the value 1.660 ×10-27 kg. Relative atomic masses (Ar) are thus all stated relative to 126C =12.0000. The masses of the proton and neutron can be considered to be ~1 u where u is the atomic mass unit
(1 u ~1.660 ×10-27 kg.).
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