large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_129
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
In fact, each different type of atom seemed associated with reflected X rays of a particular penetrating power, so Barkla called these "characteristic X rays". IN FACT EACH DIFFERENT TYPE OF ATOM SEEMED ASSOCIATED WITH REFLECTED X RAYS OF A PARTICULAR PENETRATING POWER SO BARKLA CALLED THESE CHARACTERISTIC X RAYS
ore besides. For instance, if all the electrons are removed so that only the nucleus remains, this nucleus is as massive as an atom but is so tiny in size that it can penetrate matter. The alpha particle would be a bare atomic nucleus from this point of view. Rutherford’s model of the “nuclear atom” is still accepted today. Atomic Numbers Since the atom consisted of a positively charged nucleus at the center, and a number of negatively charged electrons outside, the next step was to find the exact size of the nuclear charge and the exact number of electrons for the different varieties of atoms. The answer came through a line of research that began with the English physicist Charles Glover Barkla (1877-1944). In 1911 he noted that when X rays passed through atoms, some were absorbed and some bounced back. Those that bounced back had a certain ability to penetrate other matter. When the X rays struck atoms of high atomic weight, the X rays that bounced back were particularly penetrating. L THE ELECTRONS ARE REMOVED SO THAT ONLY THE NUCLEUS REMAINS THIS NUCLEUS IS AS MASSIVE AS AN ATOM BUT IS SO TINY IN SIZE THAT IT CAN PENETRATE MATTER THE ALPHA PARTICLE WOULD BE A BARE ATOMIC NUCLEUS FROM THIS POINT OF VIEW RUTHERFORD'S MODEL OF THE NUCLEAR ATOM IS STILL ACCEPTED TO DAY ATOMIC NUMBERS SINCE THE ATOM CONSISTED OF A POSITIVELY CHARGED NUCLEUS AT THE CENTRE AND A NUMBER OF NEGATIVELY CHARGED ELECTRONS OUTSIDE THE NEXT STEP WAS TO FIND THE EXACT SIZE OF THE NUCLEAR CHARGE AND THE EXACT NUMBER OF ELECTRONS FOR THE DIFFERENT VARIETIES OF ATOMS THE ANSWER CAME THROUGH A LINE OF RESEARCH THAT BEGAN WITH THE ENGLISH PHYSICIST CHARLES GLOVER BARCLAY EIGHTEEN SEVENTY SEVEN TO NINETEEN FORTY FOUR IN NINETEEN ELEVEN HE NOTED THAT WHEN X RAYS PASSED THROUGH ATOMS SOME WERE ABSORBED AND SOME BOUNCED BACK THOSE THAT BOUNCED BACK HAD A CERTAIN ABILITY TO PENETRATE OTHER MATTER WHEN THE X RAYS STRUCK ATOMS OF HIGH ATONIC WEIGHT THE X RAYS THAT BOUNCED BACK WERE PARTICULARLY PENETRATING
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