ATOMS AND ELECTRONS.

Otago Witness, Issue 3467, 24 August 1920, Page 51

ATOMS AND ELECTRONS.

Even 50 years ago an atom was supposed to be the only thing on earth that could not be cut in two (comments Everyday "Science). The chief reason why it has taken so long for scientists to find cut anything about the structure of atoms is that no one has ever been able to see them, so all tho work that has been done on them has been carried out, so to speak, in the dark. It has been very much like a half-blind giant, about .a. million miles high, trying to experiment with dust-shot. In’ spite of the handicap human intelligence has succeeded, not only in weighing and measuring them, but in tho last few years in actually taking them to pieces and finding out what they are made of.

The actual size and weight of an atom of hydrogen, the lightest known, if expressed in figures would have no meaning,

because it is beyond the conception even of the great minds that have done the measurements, but Lord Kelvin tried to give an idea of the size in this way. He told his students to imagine that a drop of water could be magnified until it seemed to be as large as the earth, then they would bo able to see the molecules of -water, which would appear about the size of cricket balls. They would further see that each of these molecules was made up of two atoms of hydrogen and one of oxygen. No microscope, it need hardly be said, has ever been designed, or even conceived, that can give a magnification of this kind. In 1891 Mr Johnstone Stoney gave the name "electron" to something very much smaller than an atom. It might be called an atom of electricity, and although the name is rather confusing it would be correct, because the word atom means "something that cannot be cut," and the electron has a much better right to it than the larger thing that is still so called. Perhaps it would be simpler to call the electrons "particles of electi'icity." Now, electrons are particles of negative electricity, and we know that in electricity like repels like. Just as the north pole of a magnet repels another north pole placed near it, so does a body charged wiith negative electricity repel another body charged in the same way. Therefore, it is fail' to say that if an atom was entirely made up of electrons, it would tend to fly to pieces. The modern idea of an atom is that it has in its centre a "corpuscle" of positive electricity, around which is packed a coating of electrons, attracted like flies to honey. The outer ones are not attracted so much, and move round and round, like the planets round the sun.

They resemble the planets in more ways than one. They not only move round, but they all move in one direction, and they keep very nearly in one plane. That h to say, the atom would appear, if we could see it, very much like the pictures of the planet Saturn as seen through a large telescope. The globe of the planet would represent the mass of electrons clustering tightly round the central "corpuscle," and the rings would represent the whirling mass of loose electrons flying about the positive corpuscles inside the atoms, but we know a very great deal about the moving electrons that ring them round.