large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_252
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
All 3 lead isotopes had the same atomic number of 82. ALL THREE LEAD ISOTOPES HAD THE SAME ATOMIC NUMBER OF EI
lead. In each case the lead formed was stable (not radioactive). Were the lead atoms identical in every case? Soddy had worked out the way in which atomic weights altered every time an alpha particle or a beta particle was given off by an atom. Working through the three radioactive series he decided that the lead atoms had different atomic weights in each case. The uranium series ought to end with lead atoms that had an atomic weight of 206. The thorium series ought to end in lead atoms with an atomic weight of 208 and the actinium series in lead atoms with an atomic weight of 207. If this were so, there would be 3 lead isotopes that would differ not in radioactive properties, but in atomic weight. The isotopes could be referred to as lead-206, lead-207, and lead-208. If we use the chemical symbol for lead (Pb), we could write the isotopes, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb. (We read the symbol ²⁰⁶Pb as lead-206.) Atomic weight measurements made in 1914 by Soddy and others supported that theory.  WORKED OUT THE WAY IN WHICH ATOMIC WEIGHTS ALTERED EVERY TIME AN ALPHA PARTICLE OR A BATA PARTICLE WAS GIVEN OFF BY AN ATOM WORKING THROUGH THE THREE RADIOACTIVE SERIES HE DECIDED THAT THE LEAD ATOMS HAD DIFFERENT ATOMIC WEIGHTS IN EACH CASE THE URANIUM SERIES OUGHT TO END WITH LEAD ATOMS THAT HAD AN ATOMIC WEIGHT OF TWO O SIX THE THORIUM SERIES OUGHT TO END IN LEAD ATOMS WITH AN ATOMIC WEIGHT OF TWO O EIGHT AND THE ACTINIUM SERIES IN LEAD ATOMS WITH AN ATOMIC WEIGHT OF TWO O SEVEN IF THIS WERE SO THERE WOULD BE THREE LEAD ISOTOPES THAT WOULD DIFFER NOT IN RADIOACTIVE PROPERTIES BUT IN ATOMIC WEIGHT THE ISOTOPES COULD BE REFERRED TO AS LEAD TO O SIX LEAD TO O SEVEN AND LEAD TO O EIGHT IF WE USED THE CHEMICAL SYMBOL FOR LEAD P B WE WOULD WRITE THESE ISOTOPES SUPERSCRIPT TWO O SIX P SUPERSCRIPT TO O SEVEN B AND SUPERSCRIPT TO EIGHT B WE READ THE SYMBOL SUPERSCRIPT TWO O SIX B AS LEAD TWO O SIX ATOMIC WEIGHT MEASUREMENTS MADE IN NINETEEN FOURTEEN BY SODDI AND OTHERS SUPPORTED THAT THEORY
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