On the assumptions that electrons in atoms and ions can be considered to be in hydrogen-like orbits under the influence of an effective nuclear charge $\mathrm{}(Z-s)e$, and that the screening constant $s$ is the same for ions with the same structure, there is calculated for the second ionization potential of lithium the value 76.2 v., and for the electron affinity of hydrogen atoms the value -1.85 k. cal./mol. These values are shown to lie within the range permitted by existing spectral and thermochemical data. With the use of the electron affinity of hydrogen it is shown that theoretically the hydride ion should be unstable in aqueous solution.

• Received 9 October 1926

DOI:https://doi.org/10.1103/PhysRev.29.285