In 1961 the mlar atomic mass of carbon 12 was defined to be exactly 12g/mol (a value agreed upon by chemists and physicists) and the molar atomic masses of all the elements were re-evaluated according to this new standard. this made the re-evaluated molar mass of oxygen-16 become 15.994915g/mol. avogadro's number is defined as the number of atoms in the molar atomic mass of an element. the present accpted value for avogadros' number is 6.0221367x10^23/mol. what was the value o avogadro's number used by physicists before 1961? .