Physicists atomic-weight scale

The isotopes of the elements show several interesting properties. The known isotopes for the first 10 elements are listed in Table 33-2. The masses given in column 3 of this table refer to the physicists atomic weight scale, in which O = 16.00000. 

Presently accepted definitions of masses (historically preferred by physicists) and weights (historically preferred by chemists) at the atomic scale are as follows ... 

Before the 1970s, two conventions were used for determining relative atomic masses. Physicists related their mass spectrometric determinations to the mass of (i.e. has a mass of exactly 16 on the amu scale), the most abundant isotope of oxygen, and chemists used the weighted mass of all three isotopes of oxygen and At an international congress devoted... 

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