Atomic Weights of Krypton, History

It is believed that krypton has a monatomic molecule and that the atomic weight is, consequently, identical with the molecular weight and =82.92. The reasons for this belief may be summarised briefly as follows: -

1. The ratio of the specific heats at constant pressure and constant volume approximates closely to 1.667.
2. The general properties of the gas indicate that it should occupy a position in the periodic classification of the elements between bromine (at.wt. = 80) and rubidium (at.wt. = 85.5), a position with which the atomic weight given above is in agreement.
3. The positive ray method of analysis indicates that the gas is monatomic.