Nuclear Fission

In 1939, Otto Hahn and Fritz strazzman published their work on a special kind of Nuclear reaction of both teoretical and practical interest.It was already known that many product of artificially induced transmutation were themselves radioactive.Hahn and Strassman, along with Lise meitner, had bonbarded uranium wiyh neutron. Their exprriments were similar to other experiments being done at that time in an effort to create elements of atomic number greater than 92(uranium).
The products of the reactuon were radioactive, but there was great diffculty in identifying the actual nuclei. Finally, a series of extremely careful chemical analyses by Hahn shoed that the reaction products contain both Ba(139,56) and La(140,57), two materials much lighter than uranium.
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Fisson procces have the possibility of being of some particel use because thhey have possitive Q value; that is, the kinetic energy of the product is greter than the kinetic energyof the initial reactan s. The possitive Q value occurs because the heavier elements have a smaller binding energy per nucleon than do the medium-mass elements. The heavy elements can then break up into two components that are more tightly bound and therefore have less total mass energy. On the average, about 200 MeV of energy are released per fission. Compare yhis value wiyh the average energy in chemical reactions,wich is less than 1 eV per molecule.
The large energy produced per fiddion would be of no practical use if it were not for the fact that each fiddion realeses an average of 2.5 neutrons. If we place the fissioning nuclei in the proper configuration, theseneutrons can cause other fission. The neutron from those fissions can cause still other fissions,each fisssion releasing more neutrons and more energy. Such a procces is called a chain reaction.If the procces occurs in an uncontrolled fashion, the result is an explosion. If the procces is carried out in a manner that limits the number of neutrons causing successive fission events, then the heat due to the kinetic energy can be extracted and made to he useful work, as in nuclear-fueled power plants. In either case, the products of the fisson proccess are extremely radioactive. The products are mostly long-lived gamma-ray emitters, which offer considerable health hazard.