large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_144
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
Uranium X₁, and ordinary thorium were in the same place in the list of elements by chemical standards, and yet there was clearly something different about the two. Here is another case. In 1913 the British chemist Alexander Fleck (1889  ) studied "radium B" and "radium D", the names given to two different kinds of atoms in the uranium radioactive series. URANIUM EX ONE AND ORDINARY THORIUM WERE IN THE SAME PLACE IN THE LIST OF ELEMENTS BY CHEMICAL STANDARDS AND YET THERE WAS CLEARLY SOMETHING DIFFERENT ABOUT THE TWO HERE IS ANOTHER CASE IN NINETEEN THIRTEEN THE BRITISH CHEMIST ALEXANDER FLECK BORN EIGHTEEN EIGHTY NINE STUDIED RADIUM B AND RADIUM D THE NAMES GIVEN TO TWO DIFFERENT KINDS OF ATOMS IN THE URANIUM RADIOACTIVE SERIES
e was true of thorium (atomic number 90), which began a series that also ended with lead. Still a third element, actinium (atomic number 89) was, at that time, the first known member of a series that also ended in lead. The various atoms formed in these three radioactive series were not all different in every way. When the uranium atom gives off an alpha particle, it forms an atom originally called “uranium X₁”. On close investigation, it turned out that this uranium X₁ had the chemical properties of thorium. Uranium X₁, had, however, radioactive properties different from ordinary thorium. Uranium X₁ broke down so rapidly, giving off beta particles as it did so, that half of any given quantity would have broken down in 24 days. Another way of saying this (which was introduced by Rutherford) was that the “half-life” of uranium X₁, is 24 days. Ordinary thorium, however, gives off alpha particles, not beta particles, and does so at such a slow rate, that its half-life is 14 billion years! HORIUM ATOMIC NUMBER NINETY WHICH BEGAN A SERIES THAT ALSO ENDED WITH LEAD STILL A THIRD ELEMENT ACTINIUM ATOMIC NUMBER EIGHTY NINE WAS AT THAT TIME THE FIRST KNOWN MEMBER OF A SERIES THAT ALSO ENDED IN LEAD THE VARIOUS ATOMS FORMED IN THESE THREE RADIOACTIVE SERIES WERE NOT ALL DIFFERENT IN EVERY WAY WHEN THE URANIUM ATOM GIVES OFF AN ALPHA PARTICLE IT FORMS AN ATOM ORIGINALLY CALLED URANIUM X ONE ON CLOSE EXAMINATION IT TURNED OUT THAT THIS URANIUM X ONE HAD THE CHEMICAL PROPERTIES OF THORIUM URANIUM X ONE HAD HOWEVER RADIOACTIVE PROPERTIES DIFFERENT FROM ORDINARY THORIUM URANIUM X ONE BROKE DOWN SO RAPIDLY GIVING OFF BITTER PARTICLES AS IT DID SO THAT HALF OF ANY GIVEN QUANTITY WOULD HAVE BROKEN DOWN IN TWENTY FOUR DAYS ANOTHER WAY OF SAYING THIS WHICH WAS INTRODUCED BY RUFFORD WAS THAT THE HALF LIFE OF URANIUM X ONE IS TWENTY FOUR DAYS ORDINARY THORIUM HOWEVER GIVES OFF ALPHA PARTICLES NOT BATTER PARTICLES AND DOES SO AT SUCH A SLOW RATE THAT ITS HALF LIFE IS FOURTEEN BILLION YEARS
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