“ISOTOPES”

Dominion, Volume 14, Issue 261, 29 July 1921, Page 2

“ISOTOPES”

THE CONSTRUCTION OF ATOMS. At a welbattended meeting of the chemical Section o£ the Philosophical Society, held at Victoria College, on Monday evening, Professor Marsden delivered a very interesting paper on ‘ Isotopes. The lecturer showed that atoms arc built up of positive and negative electricity. The positive electricity occupies the centre or nucleus of the atom; the negative is distributed as electrons which sur . round the central nucleus like planets surround tho sun of our s °l“ r system. The kind of atom is entirely determined bv the number of planets, and their arrangement, and this also determines flu chemical properties of the atom. hvdrogen, tho lightest element know i, has ono electron; helium has two; littium, three, and so on; the heaviest element known, oranium, having as many ns 92 electrons. Tho weight of an atom is merely an accidental number, depena-. ing on the arrangement of the electricity in the nucleus. Thus it is possible t-n have atoms with the same number ot planets and therefore the same chemical properties, yet- with different weights. This result has been experimentally proved by the brilliant work of IvUiherford. Thomson, and Aston who have proved amongst other results that there are two types of chlorine atoms; chemL callv identical, with atomic weights of 35 and 37 units. It is possible, that. the chlorine in the volcano of \V hire Island may consist of one or other or these chlorines, .mid Professor Hpbertson reported that tests on this point v’o.fld be made in the near future. The lecturer then dealt with the methods by which elements with different number, of electrons attracted and combined with each other, to produce the ordinary chemical compounds. At ths conclusion of the lecture a hearty vote of tnauKß was accorded the speaker.