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WILLIAM H. NICHOLS MLDAL AWARD grown to be, and you can therefore understand something of the great loss to this country which his giving up the teaching profession must have produced. Fortunately, he made good in other directions, and I do not doubt that his contribution to the world has been greater in the field which he has chosen than it would have been had he continued as a teacher of young men. But it frequently happens that such is not the case. I have seen men, young, splendid men, lured away from professional work into the industries, and I have seen them get smaller and smaller as time went on, and the output of the laboratory they abandoned dwindle as to quality because their places had been inadequately filled. Now you understand I am not saying these things in criticism of Dr. Langmuir, but I want to use the fact as a pretext to point out something which I consider of tremendous importance . We have had in this SOCIETY for several years a committee known as MEDAL PRESENTAthe Committee on CoTION operation between the By William H. Nichols Universities and the InGENERALCHEMICAL Co , dustries. The chairman hTsw YORK, N. Y. of that Committee is now the President of the SoThe President of the CIETY, and he has put a SOCIETY regretfully finds great deal of intelligent himself unable to be with work into the operations us to-night, and ‘assume of the Committee. I his privilege of presenting have been and am one of the SOCIETY’S medal to its members. I have Dr. Langmuir. I have been studying the work been asked to act in his of that Committee, realizplace, and assume the ing, as all of us must honor with pleasure realize, the absolute necestinged with regret that sity, in one way or our highest official should another, of getting a not be here to add digcloser relationship benity to the occasion. tween the universities He has, however, written and the industries. The a most appreciative letter. lack of cooperation may There are a t least two IRVING LANGMUIR, WILLIAMH. NICHOLS MEDALIST, 1919 possibly be likened to points in which I can the invention of the claim personal resemblance to Dr. Langmuir. We were both born in Brooklyn sewing machine. You remember how difficukt that was and we both, when we were rather young, attended public until some smart fellow happened to think that he could put the eye near the point of the needle. Then we had the sewing school, a course which I wish more American boys pursued. After that you know his history, where he was educated, the machine. Now this Committee has been working from below splendid work he did, and how, finally, after his graduation a t up with the idea of founding fellowships rather than providing Gottingen, he took up teaching a t Stevens Institute. I am for what the Fellows were to receive when they get to college. going t o ask his permission and yours to take his career as a I have come to feel that it is more important to look out for the scientist for granted and t o make use of an important decision professor who is going to teach the Fellow, although fully apof his, without in the slightest degree any criticism of it, to preciating the importance of the other point of view. point a moral to what I consider one of the vital questions As you think of it thus, you see that the position of professor before the American people to-day. Dr. Langmuir began with in the university or technical school (or for that matter, of teacher teaching, and you can all imagine what kind of a teacher he in all branches down to the primary school) has not in point of must have made, and what kind of a teacher he would have reward kept pace with the times; and the temptation which A unique situation was presented a t the Chemists’ Club, New York City, on the evening of March 5 , 1920, in that the Nichols Medal for the first time was awarded to a previous recipient. For his brilliant paper on “The Arrangement of Electrons and Atoms in the Molecule,” published in the June 1919 issue of the Journul of the A m e r i c a n Chemical Society, Dr. Irving Langmuir was awarded the medal, following a unanimous vote by the jury of the award. Dr. William H. Nichols, the founder of the medal, made the presentation in a thoughtful address and in his usual felicitous manner. In his address of acceptance, Dr. Langmuir presented a general outline of the octet theory of valence. An unexpected feature was added to the evening by the exhibition of a series of models constructed by Mr. Leffert Lefferts illustrating the structure of molecules of well-known compounds according to the theory.-- [EDITOR. ]
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comes to a perfectly capable man to yield to the allurement of industry and leave his professorial work is strong, and his embracing the opportunity thus offered is by no means discreditable. Now the industries in holding out the lure cannot realize that they are “killing the goose that lays the golden egg.” The case before us to-night is the antithesis of this, which s v w s that -every rule has its exceptions. We must think of some way to make it to the interest of the best men in the profession to teach chemistry, or the science of chemistry will suffer here in comparison with other countries, and, as all of the industry of the country rests first upon the chemical industry and that in turn upon the chemist, this means that the effect will be shown in all of our industries if we do not find some way to induce the best men to remain. What is even more important is to induce the best men on graduating to prepare to fill the places which become vacant. Now how can that be done? It is a problem of finance. Many of the colleges and universities have had, are having, or are going to have drives to make large and much needed additions to their endowment funds, and yet if they get all they ask there will not be enough in my judgment to carry out the idea which I have tried to express, of making the teaching of chemistry a t our universities and colleges not only one of the most delightful employments, one of the most heartening and loving labors, which it is now, but also one of the most attractive from the point of view of the welfare of the incumbent himself as well as that of his family. This thought had led me to the conclusion that the relation between the universities and the industries must be shown in the readiness of the industries willingly, gladly, and from a sense, if you please, of enlightened selfishness, to see to it that the good chemical professors shall be adequately and even more than adequately provided for for the present, and also for the future by annuities for old age and insurance in case of death. I believe that this is the need, to take hold of the question from the professorial end, and not from that of the student alone. Of course, there will be an abundance of splendid students. How are they going to be met when they get to the college, and what kind of teaching are they to receive? I think a plan is being devised, which is not yet advanced sufficiently to be made public, which will solve this question. I believe that before the year is out we shall see that this problem is in a fair way of solution, and that successful professors of chemistry will not only find themselves in one of the most delightful of all occupations, teaching, but that they will also be well paid. When that comes about we can all congratulate ourselves that our industries will continue to lead the world, The gentleman who is to receive the SOCIETY’S medal tonight is so well known to every one of you that words from me are unnecessary. This is not his first appearance. He received the medal in 1915. This will be his second recipiency and in this his case is so far unique. Moreover, the paper for which the Committee has awarded the medal had the distinction of being read twice a t the same meeting. When a t Buffalo it created such a sensation that he was asked to read i t again, which he did. I do not recall another instance of this. It shows that instead of the vote of the Committee it was the vote of the SOCIETY; in fact, a real referendum. Dr. Langmuir, in carrying out the very agreeable duty which lis assigned t o me, I do so with the utmost pleasure and with the right hand of fellowship. One of your qualities that we like, almost better than any other, is that you are always prepared to give credit to those who have been assisting you and to share with them the honor. It adds very much to my pleasure in presenting this medal to think that there are others who aided a n d assisted you in your splendid work, and that you generously make that claim in their behalf.
Vol.
12,
No. 4
THE STRUCTURE OF ATOMS AND ITS BEARING ON CHEMICAL VALENCE By Irving Langmuir GENERAL ELSCTRIC Co., SCRENSCTADY, NEWPORK
According to the well-established Rutherford-Bohr theory, all the positive electricity in an atom is concentrated in a nucleus a t its center. The dimensions of this nucleus are negligibly small compared with those of the rest of the atom, its diameter being of the order of O.OOOOI of that of the atom. The charge on the nucleus is an integral multiple of the charge of an electron but of course opposite in sign. The remainder of the atom consists of electrons arranged in space about the nucleus, the normal number of such electrons (called the atomic number) being equal to the number of unit positive charges on the nucleus, so that the atom as a whole is electrically neutral. If the number of electrons in the atom exceeds the atomic number we have a negatively charged atom or ion while in the reverse case a positively charged atom or ion results. The atomic number of any element has been found to be equal to the ordinal number of the element in the periodic table. Thus hydrogen has the atomic number one, helium 2, lithium 3, carbon 6 , neon IO, chlorine 1 7 , nickel 28, silver 4 7 , cerium 58, tungsten 74, radium 88, and uranium 92. The atomic numbers can be determined experimentally from the X-ray spectrum so that we are not dependent upon the periodic table for our knowledge of these numbers. Bohr, Sommerfeld, and others have developed an extensive and very successful theory of spectra upon the hypothesis that the electrons in atoms are in rapid rotation in plane orbits about the nucleus in much the same way as the planets revolve around the sun. Stark, Parson, and G. N. Lewis on the other hand, starting from chemical evidence, have assumed that the electrons are stationary in position. It should be noted that Bohr’s theory has had its greatest success when applied t o atoms or ions containing only one electron and that it seems incapable of explaining the chemical or ordinary physical properties of even such simple elements as lithium, carbon, or neon. The two theories can, however, be reconciled if we consider that the electrons, as a result of forces which they exert on one another, rotate about certain definite positions in the atom which are distributed symmetrically in three dimensions. Thus for atoms containing only a single electron the chemical theory is in agreement with Bohr’s theory. But for an atom such as neon the eight electrons in the outside layer would revolve around positions which are located about the nucleus in the same way that the eight corners of a cube are arranged about the center of the cube. This structure is not inconsistent with those parts of Bohr’s theory which have received experimental confirmation. In fact, Born and Land&’ starting from Bohr’s theory and without knowledge of Lewis’ work, arrived a t exactly this conception of the structure of atoms ( i ,e., the cubic atom) from a study of the compressibility of the salts of the alkali metals. The atomic numbers and the properties of the inert gases furnish us with a clue to the arrangement of the electrons within atoms. The low boiling point, the high ionizing potential, the chemical inertness, etc., of helium prove that the arrangement of the electrons in the helium atom is more stable than that in any other atom. Since this atom contains two electrons we must conclude that a pair of electrons in the presence of a nucleus represents a very stable group. It is reasonable that with elements of higher atomic number there should be an even greater tendency for this stable pair of electrons to form about the nucleus. There are two sets of facts which furnish conclusive experimental evidence that this stable pair exists in all atoms above helium. I n the first place, the properties of lithium, beryllium, etc.,
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Verh. d . Phrs Ges., 20 (1918), 210.
