UNSOCIABLE ATOMS.

Otago Daily Times, Issue 19102, 22 February 1924, Page 11

UNSOCIABLE ATOMS.

.ARGON? THE I/AZT GAS. CREATING A MINIATURE LONDON FOG. (From Ou.r Own Correspondent.) LONDON, January 3. Sir William Bragg, the noted scientist and Quain Professor of Physics of London University, has-been delighting a youthful audience at the Royal Institution during the Christmas week , In his opening lecture he pointed out that the whole universe, so far as we know it, is made up of 90 sorts of atoms. The atom (said Sir AVilliam) consisted of a positive nucleus, so strongly electrified, that it could hold in its orbit the minute “standard chargee or electrons which specified completely all the properties of each individual atom. How was it, he asked, that while the atoms themselves were electrically neutral, they were able to attract each other. He supplied the answer that they could be so arranged that the negative parts of one could come close to the positive parts of the other, and so make possible tho formation of compounds and the science of chemistiy. Some of the atoms had attributes similar to those of members of the human race. "Unsociable atoms,” he called them, for, hermit-like, they take little part in the world’s affairs, and refuse to associate with their neighbours. There are six of these, with electrons numbering 2, 10, 18, 36, 34, and 86 respectively. Their presence was discovered as a result of experiments conducted by the late Lord Rayleigh, when he was measuring the weight of the various constituents of the atmosphere. A minute discrepancy in his figures revealed the presence of a gas which had until then escaped observation because of its unwillingness to form compounds. This gas was named “argon” (the “lazy one”)—a title which is not adequately descriptive, since the gas moves about as quickly as any others of the same size. Its principal characteristic is its independence of behaviour. With the help of Ramsay Rayleigh worked out the properties of argon, and this led to the discovery of the others. SAFEST GAS FOR AIRSHIPS. Argon has 18 elections. The atom with two electrons is helium, the lightest of all atoms except hydrogen, which has only one. But, unlike hydrogen, helium refuses to have anything to do with its neighbours. Why the endowment of two electrons should give the atom such perfect self-satisfaction Sir William could not tell, hut it serves one very useful purpose. Hydrogen has commonly been used to fill dirigible balloons, but it has such a. strong affinity for oxygen that there is great risk of explosion; the placid existence of helium, on the other hand, cannot be disturbed, and it is immune from the perils which beset hydrogen, and for this reason it is particularly useful for airship purposes. In connection with argon, Sir William observed that it was rather curious that it had not been discovered - earlier, as The amount in the atmosphere is quits substantial. The air in the theatre of the Royal Institution, he said, weighs nearly threequarters of a ton, and in that is included argon to tho weight of about 1181 b. The other unsociable gases are “Neon” (the “new one”), “Krypton” (the “hidden one”), “Xenon” (the “Stranger”), and the gas formed by radium when it is disintegrated. The reason for the unsociability of these atoms, Sir William said, was doubtless connected with the arrangement of their electrons, suggesting a grouping in successive rings or shells round the nucleus, or their distribution on successive spheres like the coats of an onion. CREATING A LONDON FOG. Sir William showed what a very wonderful thing a gas really was. The atoms of a gas could be compared with the snooker balls on a billiard-tabß, if all of these were in rapid motion, and the cushions represented the walls of the vessel in which the gas was contained. If one of the cushions was moved so as to come closer to the opposite cushion the speed of the billiard balls was greatly increased, and exactly the same thing occurred if a gas was compressed, as could be noticed in the case of a bicycle pump, which got hot as the bicycle was pumped up. Similarly, if a gas was allowed to expand, the movement of the particles was slowed down and the gas was cooled. On the lecture table there was a great glass cylinder, and into this clean, moist air was admitted. A tap connected the cylinder to a vacuum, and, dramatically, as the connection was established, the gas in the cylinder was expanded, and cooled, with the result that particles of water were deposited in the form of a clean, white mist. The experiment was repeated in the midst of delighted applause with London air from the lecture theatre, and the children saw before them the - 'creation of a London fog in miniature, learning from the lecturer that the rapid expansion of the air over London was one of the causes of the London fog. In a further lecture Sir AVilliam Bragg explained that radium was a metal like other metals until the moment arrived when one atom or another blew up and a part of tho atom was ejected at so enormous a speed that if it were to continue unimpeded it would reach so distant an object as the moon in two seconds and a-b alt. The breakup of the radium atom in a way realised the dream of the old alchemists but the break-up of radium was uncontrolled. Heating it in a furnace did not increase the speed of breaking up; cooling did not slow it down; nothing affected it. How was it, he asked, applying to a miniature billiard table’for the answer, that the helium atom shot out 'rom radium was able to pass through the air all ' round in straight lines ? There were two obvious possibilities. Mere speed might do it, but mere speed did not. A rapidly shot billiard ball cannoned against the others and came to rest without reaching its objective. It was conceivable that the billiard ball shot out could worm its way through the others on the same lines as if you gave sixpence to a boy on one side of Piccadilly Circus with a sweet-shop on the opposite side, the boy and the sixpence would worm their way in more or less of a straight line towards the sweet shop. But this argued intelligence. Neither explanation could be accepted, and yet the facts (had to be accepted. Atoms were not coloured solid, spherical bodies or cubes, but bodies with relatively vast spaces between them. They were universes with stars and planets, and. there was no reason why one universe should not pass through another on condition that no one sun should hit another sun, and no one planet should hit another planet, in which case there would be a catastrophe.