![]() Mass of a proton ≈ Mass of a neutron ≈1 amu ( amu = atomic mass unit). They knew that ,mass of the electron is negligible and Thus, there was a lot of confusion associated with the correct method of calculation of atomic weight. Physicists were using mass spectrometry for the atomic weight analysis.Thus, they were using pure oxygen -16 isotope as standard.Chemists were using the oxide formation phenomenon for atomic weight analysis, thus they were considering naturally occuring oxygen as the standard.This naturally occurring oxygen was a mixture of three isotopes of oxygen, namely O-16,O-17 and O-18.Before 1961,physicists and chemists used two different scales to measure atomic weights.Oxygen was used as a standard, as it occurred abundantly in nature and combined with a lot of substances to form oxides.As a result of these two attributes of oxygen,carrying out chemical analysis with oxygen was easier.However, there was a discrepancy in the way physicists and chemists carried out the analysis! In Chemistry, Atomic mass and Atomic weight have different meanings too.Ītomic mass is a relative quantity as it is measured in comparison to the mass of a standard element. The quantity g is different because the earth exerts a greater pull on objects, on its surface, than the moon.This difference is attributed to the size of the earth, which is considerably large, than that of the moon. In physics, weight = mass × acceleration due to gravity.įor example, our mass remains the same on earth and moon but we would weigh less on the moon than the earth as gravitational acceleration, ‘g’, is different on earth and moon. Weight(measured in newtons) is a measure of how gravitational field acts on the mass. ![]() Mass(measured in g or kg) is a measure of quantity of a substance, whereas Generally the terms weight and mass are used synonymously, although their meanings are different. Let us now proceed further and discuss periodic trends in a new parameter – The atomic weight or atomic mass.
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