large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_159
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
It was at the moment difficult to tell in the case of lead, but an answer came in connection with another element, the rare gas neon (atomic symbol Ne), which has an atomic weight of 20. IT WAS AT THE MOMENT DIFFICULT TO TELL IN THE CASE OF LEAD BUT AN ANSWER CAME IN CONNECTION WITH ANOTHER ELEMENT THE RARE GAS NEEON ATOMIC SYMBOL N E WHICH HAS AN ATOMIC WEIGHT OF TW
had nuclei with an electric charge of +82 and all 3 had 82 electrons in the atom to balance that positive nuclear charge. The difference was in the mass of the nucleus only. [Illustration: _Isotopes of two elements._] Atomic number, 1 Hydrogen-1: Mass number, 1; 1 Proton, 1 Electron Hydrogen-2: Mass number, 2; 1 Proton, 1 Neutron, 1 Electron Atomic number, 2 Helium-3: Mass number, 3; 2 Protons, 1 Neutron, 2 Electrons Helium-4: Mass number, 4; 2 Protons, 2 Neutrons, 2 Electrons But what of ordinary lead that existed in the rocks far removed from any radioactive substances and that had presumably been stable through all the history of earth? Its atomic weight was 207.2. Was the stable lead that had no connection with radioactivity made up of atoms of still another isotope, one with a fractional atomic weight? Or could stable lead be made up of a mixture of isotopes, each of a different whole-number atomic weight and was the overall atomic weight a fraction only because it was an average? PERSCRIPT 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 ALL THREE LEAD ISOTOPES HAD THE SAME ATOMIC NUMBER OF EIGHTY TWO THE ATOMS OF ALL THREE ISOTOPES HAD NUCLEI WITH AN ELECTRIC CHARGE OF PLUS EIGHTY TWO AND ALL THREE HAD EIGHTY TWO ELECTRONS IN THE ATOM TO BALANCE THAT POSITIVE NUCLEAR CHARGE THE DIFFERENCE WAS IN THE MASS OF THE NUCLEUS ONLY BUT WHAT OF ORDINARY LEAD THAT EXISTED IN THE ROCKS FAR REMOVED FROM ANY RADIOACTIVE SUBSTANCES AND THAT HAD PRESUMABLY BEEN STABLE THROUGH ALL THE HISTORY OF EARTH ITS ATOMIC WEIGHT WAS TWO O SEVEN POINT TWO WAS THE STABLE LEAD THAT HAD NO CONNECTION WITH RADIOA ACTIVITY MADE UP OF ATOMS OF STILL ANOTHER ISOTOPE ONE WITH A FRACTIONAL ATOMIC WEIGHT OR COULD STABLE LEAD BE MADE UP OF A MIXTURE OF ISOTOPES EACH OF A DIFFERENT WHOLE NUMBER ATOMIC WEIGHT AND WAS THE OVERALL ATOMIC WEIGHT A FRACTION ONLY BECAUSE IT WAS AN AVERAGE
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