New pathways in science / by Sir Arthur Eddington.

  • Eddington, Arthur Stanley, Sir, 1882-1944.
Date:
1935
Catalogue details

Licence: In copyright

Credit: New pathways in science / by Sir Arthur Eddington. Source: Wellcome Collection.

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    I electron, so that it is of atomic weight 2; the net nuclear charge is i, and there is just one sateUite electron as in ordinary hydrogen. By the usual rule the two isotopes would not be entitled to separate chemical names; but the circumstances are rather exceptional, and heavy hydrogen has been named deuterium (or by some writers, diplogen) and given a chemical symbol D. Its nucleus, when it occurs without the sateUite electron, is caUed a deuton (or diplon). The difference between hydrogen and deuterium (of respective weights I and 2) is not such a trivial matter as the difference between most isotopes; and deuterium and its compounds have appreciably different properties from hydrogen and its compounds. NaturaUy the compound DzO, or heavy water, has received special attention; it is 11 per cent, heavier than ordinary water (HjO). A stiU heavier hydrogen of atomic weight 3 has also been discovered; its nuclei (tritons ?) consist of 3 protons and 2 electrons. Another recent discovery is the neutron. This appears to be a nucleus consisting of i proton and i electron, so that the net charge is zero and there are no sateUite electrons. It is thus an element of atomic number o. We might describe it as an isotope of nothing. From another point of view the neutron is a kind of coUapsed hydrogen atom; both consist of a proton and an electron, the difference being that in the neutron they are held close together by nuclear binding and in the hydrogen atom more distantly by sateUite binding. One of the questions we ask ourselves is whether hydrogen atoms ever spontaneously coUapse into neutrons.* Another very famihar particle is the a particle, f It is the nucleus of a heUum atom (atomic number 2) consisting of * According to some experimenters the mass of a neutron is rather greater than that of a hydrogen atom. If so, it contains more energy, so that its formation involves an absorption of energy and is not of the nature of a spontaneous collapse. f A j8 particle is merely a fast-moving electron.