Resonance in the Hydrogen Molecule

In a recent paper (1) Mueller and Eyring have discussed the normal state of the hydrogen molecule with use of a variation function constructed in the usual Heitler-London manner, except with replacement, for each electron, of the hydrogen-atom function about atom a, exp(-Z'ra/ao), byt the more complex function φa = exp(-Z'ra/ao)exp(-Z''rb/a0). The authors call one-electron functions of this sort semilocalized orbitals. They have compared the value of the bond energy calculated for the wave function [...], with those given by the simple atomic orbital method and the molecular orbital method, and have pointed out that there is an improvement to 4.20 ev, from the values 3.76 ev and 3.60 ev, respectivel

Interatomic Distances in Covalent Molecules and Resonance between Two or More Lewis Electronic Structures

In a paper to be published in the Zeitschrift für Kristallographie, Professor M. L. Huggins and I have formulated tables of radii for use in crystals containing electron-pair bonds. With the aid of these tables, we have also constructed a table of radii (table 1) for non-metallic atoms in covalent molecules. These radii are designed especially for purely covalent compounds, in which fluorine forms one electron-pair bond, oxygen two, nitrogen three, etc., but they are applicable also to other compounds, such as (CH3)3N:O:, with the following exception. The radii given for As, Se, Br, Sb, Te and I are to be used for these atoms with a covalence of one, two or three; for a covalence of four slightly smaller values ("tetrahedral radii") are to be used. The change is probably due to a change in the nature of the bond eigenfunctions involved

Academic Research as a Career

The real student in science — with a consuming curiosity into the laws of nature and with top scholastic status — may be of the caliber required to become the recognized authority in some fiel

Molecular Architecture and Biological Reactions

Answers to many basic problems of biology—nature of growth, mechanism of duplication of viruses and genes , action of enzymes, mechanism, of physiological activity of drugs, hormones, and vitamins, structure and action of nerve and brain tissue—may lie in knowledge of molecular structure and intermolecular reactions

Analogies between Antibodies and Simpler Chemical Substances

Because of his contributions in the study of antibodies, Linus Pauling was chosen as the first Harrison Howe lecturer. His talk, given below, was delivered before the Rochester Section of the American Chemical Society, Feb. 4, in Rochester, Ν. Υ

The effects of strontium-90 on mice

On Sept. 19, 1958 there was published in Science a paper by Dr. Miriam P. Finkel of Argonne National Laboratory in which she communicated her observations on the effects of strontium-90 injected into mice on life expectancy and on incidence of tumors of bone and blood-forming tissues.(1) She discussed the question of whether or not the effects are proportional to the amount of injected strontium-90 at low doses, and reached the conclusion that it is likely that there is a threshold with value for man between 5 and 15 μc. (as compared with the present average value from fallout, about 0.0002 μc., and the predicted steady-state value from fallout for testing of nuclear weapons at the average rate for the past five years, about 0.02 μc.). Her paper ends with the sentence "In any case, the present contamination with strontium-90 from fallout is so very much lower than any of these levels that it is extremely unlikely to induce even one bone tumor or one case of leukemia.

Priestley Medal Address: Chemistry and the World of Tomorrow

This article is based on the Priestley Medal Address presented by Linus C. Pauling on April 9, during the ACS spring meeting in St. Louis. Still active at 83, Pauling is director of the Linus Pauling Institute of Science & Medicine, Palo Alto, Calif., where he continues his scientific research. Much of his work has dealt with the nature of the chemical bond. The Priestley Medal, ACS's highest award, recognizes his contributions in this and other areas, and is the latest in a long list of honors and awards Pauling has received, including the 1954 Nobel Prize in Chemistry and the 1962 Nobel Peace Prize

Unsolved Problems of Structural Chemistry

Linus Pauling, Theodore William Richards Medalist for 1947, has made notable contributions to quantum mechanics, valence theory, crystal structure, and also to electron diffraction

The Additivity of the Energies of Normal Covalent Bonds

The chemical bond between two identical atoms, as in the molecules H2, Cl2, etc., may be considered as an example of a normal covalent bond, involving an electron pair shared by the two atoms. The wave function representing this bond cannot necessarily be closely approximated by a function of the Heitler-London type, with the electrons staying on different atoms, but may contain ionic terms, corresponding to the two electrons of the bond on the same atom, the term representing the configuration A+A- occurring, of course, with the same coefficient as that for A -A +. The contribution of these ionic terms to the wave function for the normal state of the hydrogen molecule has been discussed by Slater [1]

The modern theory of valency

NEARLY 100 years ago, in 1852, it was stated for the first time, by E. Frankland, that atoms have a definite combining power, which determines the formulas of compounds. Then in 1858 Archibald S. Couper introduced the idea of the valency bond and drew the first structural formulas, and August Kekulé showed that carbon is quadrivalent. This simple valency-bond theory permitted great progress to be made in structural organic chemistry, but structural inorganic chemistry remained largely undeveloped until the present century. With the discovery of the electron and the elucidation of the electronic structure of atoms, it became possible for Gilbert Newton Lewis in 1916 to identify the covalent bond with a pair of electrons shared by two atoms and counting as part of the outer shell of each, and thus to lay the basis for the development of the modern theory of valency, to which Sidgwick, Robinson, and many other chemists have contributed. The modern theory of valency is not simple-it is not possible to assign in an unambiguous way definite valencies to the various atoms in a molecule or crystal. It is instead necessary to dissociate the concept of valency into several new concepts-ionic valency, covalency, metallic valency, oxidation number-that are capable of more precise treatment; and even these more precise concepts in general involve an approximation, the complete description of the bonds between the atoms in a molecule or crystal being given only by a detailed discussion of its electronic structure. Nevertheless, these concepts, of ionic valency, covalency, etc., have been found to be so useful as to justify our considering them as constituting the modern theory of valency