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large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
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12904
The total charge would then be 0 and the atom as a whole would be electrically neutral. THE TOTAL CHARGE WOULD THEN BE ZERO AND THE ATOM AS A WHOLE WOULD BE ELECTRICALLY NEUTRAL
m, gave off positively charged alpha particles. Many atoms, however, that were not radioactive, could be made to give off electrons. In 1899 Thomson showed that certain perfectly normal metals with no trace of radioactivity gave off electrons when exposed to ultraviolet light. (This is called the “photoelectric effect”.) It was possible to suppose, then, that the main structure of the atom was positively charged and generally immovable, and that there were also present light electrons, which could easily be detached. Thomson had suggested, as early as 1898, that the atom was a ball of matter carrying a positive charge and that individual electrons were stuck throughout its substance, like raisins in pound cake. If something like the Thomson view were correct then the number of electrons, each with one unit of negative electricity, would depend on the total size of the positive charge carried by the atom. If the charge were +5, there would have to be 5 electrons present to balance that.  CHARGED ALPHA PARTICLES MAN ATOMS HOWEVER THAT WERE NOT RADIOACTIVE COULD BE MADE TO GIVE OFF ELECTRONS IN EIGHTEEN NINETY NINE THOMPSON SHOWED THAT CERTAIN PERFECTLY NORMAL METALS WITH NO TRACE OF RADIO ACTIVITY GAVE OFF ELECTRONS WHEN EXPOSED TO ULTRA VIOLET LIGHT THIS IS CALLED THE PHOTO ELECTRIC EFFECT IT WAS POSSIBLE TO SUPPOSE THEN THAT THE MAIN STRUCTURE OF THE ATOM WAS POSITIVELY CHARGED AND GENERALLY IMMOVABLE AND THAT THERE WERE ALSO PRESENT LIGHT ELECTRONS WHICH COULD EASILY BE DETACHED THOMPSON HAD SUGGESTED AS EARLY AS EIGHTEEN NINETY EIGHT THAT THE ATOM WAS A BALL OF MATTER CARRYING A POSITIVE CHARGE AND THAT INDIVIDUAL ELECTRONS WERE STUCK THROUGHOUT ITS SUBSTANCE LIKE RAISINS IN POUND CAKE IF SOMETHING LIKE THE THOMSON VIEW WERE CORRECT THEN THE NUMBER OF ELECTRONS EACH WITH ONE UNIT OF NEGATIVE ELECTRICITY WOULD DEPEND ON THE TOTAL SIZE OF THE POSITIVE CHARGE CARRIED BY THE ATOM IF THE CHARGE WERE PLUS FIVE THERE WOULD HAVE TO BE FIVE ELECTRONS PRESENT TO BALANCE THAT
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