Atomic Weights of Neon, History

The atomic weight of neon is believed to be identical with its molecular weight, which is, as has already been mentioned, taken as 20.20. The reasons for this belief may be summarised briefly as follows: -

1. The ratio of the specific heats at constant pressure and constant volume is 1.64;
2. The gas has an extremely small dielectric cohesion Helium, and Argon;
3. The evidence of the positive-ray method.
4. The general relationship of the element to the other inert gases and to other elements indicate that it should properly occupy the position in the periodic classification between fluorine and sodium into which it naturally falls if its atomic weight is taken as 20.20.