On the constitution of atoms and molecules

by Niels Bohr

considered in [§2], which gives a kind of measure for the stability for displacements perpendicular to this plane, is thus for the outer electron in lithium only

, while for hydrogen it is

. This may have a bearing on the explanation of the apparent tendency of lithium atoms to take a positive charge in chemical combinations with other elements.

For a possible negatively charged lithium atom we may expect the configuration:

It should be remarked that we have no detailed knowledge of the properties in the atomic state, either for lithium or hydrogen, or for most of the elements considered below.