depend upon these inner electrons will be carried unchanged by the atom into its chemical compounds. The properties of the real atom are in accordance with these suggestions. By far the larger number of the properties of the atom are of the constitutive type which we have associated with the outer belt of electrons. There are, however, as we have seen, other properties of the atom which are intrinsic to it; these we associate with the inner layer of electrons.
The relation between these two types of properties and the atomic weights are very different. The first type, that depending on the outer layer of electrons, waxes and wanes as we proceed along the list of elements in the order of their atomic weights; this is illustrated by the curve in Fig. 1, which represents the variation with the atomic weight of the heat of combination of the element with chlorine. The relation between an intrinsic property of the atom and its atomic weight is