large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_130
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
English
12904
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. 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
maller than any atom. Then, the investigations into radioactivity had shown that atoms of uranium and thorium spontaneously broke up into smaller particles, including electrons and alpha particles. It would seem, then, that atoms of these elements and, presumably, of all elements, were made up of still smaller particles and that among these particles were electrons. The atom had a structure and physicists became interested in discovering exactly what that structure was. The Structure of the Atom Since radioactive atoms gave off either positively charged particles or negatively charged particles, it seemed reasonable to assume that atoms generally were made up of both types of electricity. Furthermore, since the atoms in matter generally carried no charge at all, the normal “neutral atom” must be made up of equal quantities of positive charge and negative charge. It turned out that only radioactive atoms, such as those of uranium and thorium, gave off positively charged alpha particles.  LEAST MIGHT BE FAR SMALLER THAN ANY ATOM THEN THE INVESTIGATIONS INTO RADIOA ACTIVITY HAD SHOWN THAT ATOMS OF URANIUM ANTHORIUM SPONTANEOUSLY BROKE UP INTO SMALLER PARTICLES INCLUDING ELECTRONS AND ALPHA PARTICLES IT WOULD SEEM THEN THAT ATOMS OF THESE ELEMENTS AND PRESUMABLY OF ALL ELEMENTS WERE MADE UP OF STILL SMALLER PARTICLES AND THAT AMONG THESE PARTICLES WERE ELECTRONS THE ATOM HAD A STRUCTURE AND PHYSICISTS BECAME INTERESTED IN DISCOVERING EXACTLY WHAT THAT STRUCTURE WAS THE STRUCTURE OF THE ATOM SINCE RADIOACTIVE ATOMS GAVE OFF EITHER POSITIVELY CHARGED PARTICLES OR NEGATIVELY CHARGED PARTICLES IT SEEMED REASONABLE TO ASSUME THAT ATOMS GENERALLY WERE MADE UP OF BOTH TYPES OF ELECTRICITY FURTHERMORE SINCE THE ATOMS IN MATTER GENERALLY CARRIED NO CHARGE AT ALL THE NORMAL NEUTRAL ATOM MUST BE MADE UP OF EQUAL QUANTITIES OF POSITIVE CHARGE AND NEGATIVE CHARGE IT TURNED OUT THAT ONLY RADIOACTIVE ATOMS SUCH AS THOSE OF URANIUM AND THORIUM GAVE OFF POSITIVELY CHARGED ALPHA PARTICLES
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