April 5, 1937
Dr. John Arthur Wilson
757 North Broadway
Milwaukee, Wisconsin
Dear Dr. Wilson:
There is in existence a good bit of evidence that ammonium compounds such as ammonium chloride involve no sharing of electrons between nitrogen and the chloride ion. For example, in crystalline ammonium chloride it is known that the four chlorine atoms are arranged tetrahedrally around nitrogen and that the chlorine atom is no closer to one nitrogen atom than to any one of seven others, the eight being all too far away to permit formation of a shared electron pair bond with nitrogen. I am sure that you would find these questions discussed in Lewis' book or in Sidgwick's book ("The Electronic Theory of Valency", Oxford) in a satisfactory manner.
With best regards, I am
Sincerely yours,
Linus Pauling
LP:mrl