Transcription of Chapter Twelve ATOMS
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INTRODUCTIONBy the nineteenth century, enough evidence had accumulated in favour ofatomic hypothesis of matter. In 1897, the experiments on electric dischargethrough gases carried out by the English physicist J. J. Thomson (1856 1940) revealed that ATOMS of different elements contain negatively chargedconstituents (electrons) that are identical for all ATOMS . However, ATOMS on awhole are electrically neutral. Therefore, an atom must also contain somepositive charge to neutralise the negative charge of the electrons. But whatis the arrangement of the positive charge and the electrons inside the atom?
1937) British physicist who did pioneering work on radioactive radiation. He discovered alpha-rays and beta-rays. Along with Federick Soddy, he created the modern theory of radioactivity. He studied the ‘emanation’ of thorium and discovered a new noble gas, an isotope of radon, now known as thoron. By scattering alpha-rays from the metal ...
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