large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_251
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
This work of Rutherford and Soddy began a line of investigation that by 1907 had shown that there was a whole radioactive chain of elements, each one breaking down to the next in line by giving off either an alpha particle or a beta particle, until finally a lead atom was formed that was not radioactive. THIS WORK OF RUTHORD AND SODDY BEGAN A LINE OF INVESTIGATION THAT BY NINETEEN O SEVEN HAD SHOWN THAT THERE WAS A WHOLE RADIOACTIVE CHAIN OF ELEMENTS EACH ONE BREAKING DOWN TO THE NEXT IN LINE BY GIVING OFF EITHER AN ALPHI PARTICLE OR A BEETA PARTICLE UNTIL FINALLY A LEAD ATOM WAS FORMED THAT WAS NOT RADIOACTIVE
5, 85, 87, and 91 were still not known. By 1945, all seven had been discovered. It quickly turned out that the atomic number was more fundamental and more characteristic of a particular element than was the atomic weight. [Illustration: _Niels Bohr_] [Illustration: _Bohr’s study._] Since Dalton’s time it had been assumed that all the atoms of a particular element were of equal atomic weight and that atoms of two different elements were always of different atomic weight. The first inkling and the first proof that this might not be so came through the study of radioactivity. [Illustration: showing Helium atom, Hydrogen atom; Nucleus, Proton, Neutron, Electron labelled] Isotopes In 1902 Rutherford and his co-worker Frederick Soddy (1877-1956) showed that when uranium atoms gave off alpha particles, a new kind of atom was formed that was not uranium at all. It was this new atom that was eventually found to give off a beta particle, and then another atom of still another element was formed.  AT LEAST ELEMENTS WITH ATOMIC NUMBERS OF FORTY THREE SIXTY ONE SEVENTY TWO SEVENTY FIVE EIGHTY FIVE EIGHTY SEVEN AND NINETY ONE WERE STILL NOT KNOWN BY NINETEEN FORTY FIVE ALL SEVEN HAD BEEN DISCOVERED IT QUICKLY TURNED OUT THAT THE ATOMIC NUMBER WAS MORE FUNDAMENTAL AND MORE CHARACTERISTIC OF A PARTICULAR ELEMENT THAN WAS THE ATOMIC WEIGHT SINCE DALTON'S TIME IT HAD BEEN ASSUMED THAT ALL THE ATOMS OF A PARTICULAR ELEMENT WERE OF EQUAL ATOMIC WEIGHT AND THAT ATOMS OF TWO DIFFERENT ELEMENTS WERE ALWAYS OF DIFFERENT ATOMIC WEIGHT THE FIRST INKLING AND THE FIRST PROOF THAT THIS MIGHT NOT BE SO CAME THROUGH THE STUDY OF RADIOACTIVITY ISOTOPES IN NINETEEN O TWO RUTHERFORD AND HIS CO WORKER FREDERIC SODDY EIGHTEEN SEVENTY SEVEN NINETEEN FIFTY SIX SHOWED THAT WHEN URANIUM ADAMS GAVE OFF ALPHA PARTICLES A NEW KIND OF ATOM WAS FORMED THAT WAS NOT URANIUM AT ALL IT WAS THIS NEW ATOM THAT WAS EVENTUALLY FOUND TO GIVE OFF A BATTER PARTICLE AND THEN ANOTHER ATOM OF STILL ANOTHER ELEMENT WAS FORMED
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