Hi everyone, This is really annoying me, so, I am aware of the story why oxygen was replaced with carbon-12, (because chemists were using natural occurring oxygen which was a mix of oxygen-16,17,18 and therefor was an avg?, but physicists wanted pure, isolated oxygen-16 so there was two tables with two different atomic masses). But, why was carbon-12 agreed to be the new element to which all other elements masses would be compared to? -Is it because carbon-12 is the most abundant isotope (I think 98.9%?) therefore both parties (chemists, physicists) can use natural occurring carbon and get an accurate measurement without using an isolated carbon atom? Also, is how the discovery of how many nucleons there was in an atom, by comparing masses?