STRUCTURE GF ATOMS

Wanganui Chronicle, Volume LXXXI, Issue 19048, 27 June 1924, Page 8

STRUCTURE GF ATOMS

SOLAR SYSTEMS. ELECTRICAL BASIS OF MATTER. Although an atom has been likened to a solar system, there is the differ encc that if some great star came shooting into the solar system it would never be tbe same agin, while an atom can be bombarded with electrons and' shortly recover its previous state, Sir Ernest Rutherford, president of the British Association for the Advancement of Science, declares iu a statement prepared for the engineering foundation of New York. Explaining the electrical structure at matter. Professor Rutherford sayss—“All men deal with matter in the gross, and our bidics are of it constructed. Myste ) cs of matter, therefore, have a fascination for thoughtful laymen, as well as scientists an* technologists. The atom has long been familiar as the ultimate unit of matter.

“While the vaguest ideas were nald as to the possible structure of atoms, there was a general belief '- more philosophically minded that the atom could not be regarded as simrd« uncpnnccted units. For the clarifying of these somewhat vague ideas the proof in 1897 of the independent existence of the elctron as a mobile electrified unit, of mass minute compared with that of the lightest atom, was of extraordinary importance. “Our whole conception of the atom was revolutionised by the study of radio-activity. The discovery of radium provided the experimenter with powerful sources of radiation, specially suitable for examining the nature of the characteristic radiations emitted oy the radio-active In lies in general. The wonderful succession of c hangea that occur in uranium, more than thirty in number, was soon disclose].

“It was early sumised that electricity was atomic in nature. This view was confirmed and extended by a study of the charges of electricity car ried by electrons. Skilful experiments by physicists added to the knowledge of the subject. One of the main difficulties has been the uncertainty as to the relative part played by positive and negative electricity in the structure of the atom. The elctron has a negative charge of one fundamental unit. There is the strongest evidence that the atoms of matter are built up uf these two electrical units.

“It may be of interest to try to visualise the conception of the we have so far reached by taking tor illustration the heaviest atom, urari ium. At the centre of the atom is a minute nucleus surrounded by a swirling group of 92 electrons, all in motion in definite orbits, and occupying, but by no means filling, a volume of very large compared with that of the nucleus. Some of the electrons describe nsiariy circular orbits, round the nucleus; others, orbits, of a more elliptical shape, whose axes rotate rapidly round the nucleus. The motion of the electrons in the different groups is not necessarily confined to a definite region of the atom, but the electrons of one group may penetrate deeply into the region mainly occupied by another group, thus giving a type of in- 4 ter-connection or coupling between the various groups. The maximum speed of any electron depends on th closeness of the approach to the nucleus, but the outermost electron will have a minimum speed of more than 600 miles per second, while the innermost electrons have an average speed of more than 90,000 miles per second or half the the speed of light. “The nucleus atom has often been likened to a solar system, where the sun corresponds to the nucleus and the planets to the electrons. The analogy however, must not be pressed too far. Suppose, for example, we imagined that some large and swift celestial visitor traverses and escapes from our solai system without any catstrophe to itself or the planets. There will inevitably result permanent changes in ths lengths of the months and year, and our system will never return to its original state. Contrast this with the effect of shooting an electron through the electronic structure of the atom. The motion of any of the electrons will be disturbed by its passage, and in special cases an electron may be removed from its orbit and hurled out of its atomic system. In a short time another electron will fall into the vacant place from one of the outer groups, and this vacant place in turn will be filled up, and so on until the atom is again reorganised. In all cases the final state of the electronic system is the same as in the beginning.”