large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_117
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
Thus, when Moseley first presented scientists with the atomic number it turned out that there were still 7 elements that were not discovered. THUS WHEN MOSELY FIRST PRESENTED SCIENTISTS WITH THE ATOMIC NUMBER IT TURNED OUT THAT THERE WERE STILL SEVEN ELEMENTS THAT WERE NOT DISCOVERED
he positive charge on its nucleus. The atomic number could then be set equal to that charge and be made independent of new discoveries of elements. Hydrogen, for instance, has an atomic number of 1. Its nucleus carries a unit positive charge, +1, and the hydrogen atom possesses 1 electron to balance this. Helium, with an atomic number of 2, has a nuclear charge of +2 and 2 electrons, with a total charge of -2, to balance it. (The alpha particle released by radioactive atoms is identical with a helium nucleus.) The atomic number increases as one goes up the line of atoms. Oxygen atoms, for instance, have an atomic number of 8 and iron atoms have one of 26. At the upper end, thorium is 90 and uranium is 92. Each uranium atom has a nucleus bearing a charge of +92 and contains 92 electrons to balance this. Once the notion of the atomic number was worked out, it became possible to tell for certain whether any elements remained as yet undiscovered and, if so, where in the list they might be. UMBER COULD THEN BE SET EQUAL TO THAT CHARGE AND BE MADE INDEPENDENT OF NEW DISCOVERIES OF ELEMENTS HYDROGEN FOR INSTANCE HAS AN ATOMIC NUMBER OF ONE ITS NUCLEUS CARRIES A UNIT POSITIVE CHARGE PLUS ONE AND THE HYDROGEN ATOM POSSESSES ONE ELECTRON TO BALANCE THIS HELIUM WITH AN ATOMIC NUMBER OF TWO HAS A NUCLEAR CHARGE OF PLUS TWO AND TWO ELECTRONS WITH A TOTAL CHARGE OF MINUS TWO TO TO BALANCE IT THE ALPHA PARTICLE RELEASED BY RADIOACTIVE ATOMS IS IDENTICAL WITH A HELIUM NUCLEUS THE ATOMIC NUMBER INCREASES AS ONE GOES UP THE LINE OF ATOMS OXYGEN ATOMS FOR INSTANCE HAVE AN ATOMIC NUMBER OF EIGHT AND IRON ATOMS HAVE ONE OF TWENTY SIX AT THE UPPER END THORIUM IS NINETY AND URANIUM IS NINETY TWO EACH ERRANIUM ATOM HAS A NUCLEUS BEARING A CHAR OF PLUS NINETY TWO AND CONTAINS NINETY TWO ELECTRONS TO BALANCE THIS ONCE THE NOTION OF THE ATOMIC NUMBER WAS WORKED OUT IT BECAME POSSIBLE TO TELL FOR CERTAIN WHETHER ANY ELEMENTS REMAINED AS YET UNDISCOVERED AND IF SO WHERE IN THE LIST THEY MIGHT BE
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