UNIVERSITY OF CALIFORNIA
DEPARTMENT OF CHEMISTRY
May 1, 1928
Professor Linus Pauling,
California Institute of Technology,
My dear Pauling:
I am getting to be an abominable correspondent, but I hope this will not
discourage you from writing to me from time to time, as you have done, and telling
me of the things you are doing. When I received your recent letter I meant to reply
in some detail regarding the paper which you were good enough to enclose and which
I have just seen in the Proceedings. I have been wanting to think about these things
myself, but just at present I have been entirely submerged in problems of quantum
statistics with Dr. Mayer. Whether we shall get anywhere is a problem.
I was, however, very much interested in your paper as I had been in London's,
and there is much in both papers with which I an agree. The success of Pauli's principle
in the interpretation of complex spectra seemed to leave the physicists no excuse
for not accepting in its entirety the theory of paired electrons, coupled, whether
or not they constitute a bond, by the mutual neutralization of their magnatio moments;
and it will be interesting to see whether it is going to be possible to obtain any
facts from the Pauli principle or from the new mechanics regarding chemical compounds
which are not known to or not yet interpreted by chemists. Of course the fundamental
problem after the pairing of electrons is accepted is this: why can we have only one
pair in the K shell and only four pairs in the L shell, etc.?
I am sorry that in one regard my idea of valence has never been fully accepted.
It was an essential part of my original theory that the two electrons in a bond completely
lost their identity and can not be traced back to the particular atom or atoms from
which they have come; furthermore that this pair of electrons is the only thing which
we are justified in calling a bond. Failure to recognize this principle is responsible
for much of the confusion now prevailing in England on this subject, where they still
talk of polar bonds and semi-polar bonds, and so on. I think in London's paper and
in yours a little too much emphasis is placed upon the origin of the paired electrons.
I am sure that you and London are wrong in thinking that hydrogen does not
have two bonds, but this is because
neither of you has considered the possibility that in a highly polar molecule the
bond attaching hydrogen may not be in the K level of the hydrogen but in the Level.
This question is discussed briefly in my book on "Valence."
I am going abroad for a short time this summer, but shall not leave Berkeley until
the middle of June. I hope you will not be coming through Berkeley before then ad
Ithat I will have a chance to talk with you.
With kindest regards, I am,
Yours very sincerely