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ATOM IN MODERN SCIENCE
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decay But the spontaneous decay is so slow-say one or two atoms in a gram of gold or mercury in many centuries compared to several thousand per second per gram in uranium-that the most sensitive physical instrument cannot record it
The discovery of radio activity proved the complexity of nuclear structure beyond any doubt and paved the way for artificial nuclear transformations Earlier, bombardment of the nuclei by artificially accelerated charged particles such as alpha, protons, etc, was the method employed for nuclear transformations But the electric charges carried by such particles caused them to lose much of its kinetic energy while passing through the atomic bodies and prevented them from coming sufficiently close to nuclei of the bombarded material The bullets to be used for more efficient bombardment are neutrons which because they do not have an electric charge, can penetrate the heavily fortfied electrical wall surrounding the positively charged nuclei Just as coal fire nceds oxygen to keep it going,a nuclear fire needs the neutrons to maintain it But uncharged projectiles viz, neutrons are not easily available in free form as they are tightly locked up within the nuclei of atoms and recaptured as soon as they are kicked out There is only one way to sustain the nuclear reaction and that is to crcate a selfmultiplication process ie each bombarding ncutron must liberate more than one other neutron which in their turn would act as bullets
Latc in 1938 Rahn and Strassman discovered that atomic energy can be released through the fission process of uranium nuclei Luke the two pieces of a brohen spring, the two hales of a broken heavy nuclcus begin their existence in a statc of violcni
