Neutron continued discovery

Another kind of particle and another kind of interaction were discovered from a detailed study of beta radioactivity in which electrons with a continuous spectrum of energies are emitted by an unstable nucleus. The corresponding interactions could be viewed as being due to the virtual transmutation of a neutron into a proton, an electron, and a new neutral particle of vanishing mass called the neutrino. The theory provided such a successful systematization of beta decay rate data for several nuclei that the existence of the neutrino was well established more than 20 years before its experimental discovery. The beta decay interaction was very weak even compared to the electron-photon interaction. 

Although many new compounds have been discovered, the ones of most interest continue to be salts of TCNQ and compounds related to KCP, with TTF-TCNQ still attracting the greatest attention and continuing to exhibit the most unusual properties. Major developments during the past year have been the discovery in TTF-TCNQ by X-rays (INV 6) of lines showing CDW s at 4kp, and by neutron scattering (INV 16) the remarkable phase transitions at 34, 49 and 38 K. 

Perrier and Segre received new specimens of irradiated molybdenum and continued their studies. Their discovery was confirmed by other scientists. By 1939 it was understood that bombardment of molybdenum with deutrons or neutrons produces at least five technetium isotopes. Half-lives of some of them were sufficiently long to make possible substantial chemical studies of the new element. It no longer sounded fantastic to speak about the chemistry of element 43 . But all attempts to measure accurately the half-lives of the technetium isotopes failed. The available estimates were disheartening since none of them exceeded 90 days and this put a stop to.all hopes of finding the element on Earth. 

The actinides uranium and thorium occur in nature as primordial matter. Actinium and protactinium occur in nature as daughters of thorium and uranium, while small amounts of neptunium and plutonium are present as a result of neutron-capture reactions of uranium. All other members of the series are man-made. Separation chemistry has been central to the isolation and purification of the actinides since their discovery. The formation of the transplutonium actinides was established only as a result of chemical-separation procedures developed specifically for that purpose. The continued application of separation science has resulted in the availability of weighable quantities of the actinides to fermium. Separation procedures are central to one-atom-at-a-time chemistry used to identify synthetic trans-actinide (superheavy) elements to element 107 and above (Report of a Workshop on Transactinium Science 1990). 

Since the time of Rutherford, physicists have learned much about the detailed composition of atomic nuclei. In the course of these discoveries the list of particles that make up nuclei has grown long and continues to increase. As chemists, we can take a very simple view of the atom because only three subatomic particles— the proton, neutron, and electron— have a bearing on chemical behavior. 

The discovery of quantum mechanics challenged the idea that our universe behaves deterministically. Electrons, and all other small particles such as protons and neutrons, do not appear to behave deterministically. An outfielder chasing an electron could not predict where it would land. The subatomic world is indeterminate-the present does not determine the future. This was a new idea. Erwin Schrodinger himself once said of quanfum mechanics, "I don t like it, and I am sorry I ever had anything to do with it," and Neils Bohr said, "anyone who is not shocked by quantum mechanics has not understood it." To some, an indeterminate universe was threatening. To others, the idea that the future was not predetermined-at least for subatomic particles-came as a pleasant surprise. In philosophy, the debate continues. However, the indeterminate nature of the subatomic world dealt a severe blow to the idea that every event in the universe is determined by the event before it. 

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