e same, but the added or subtracted weight may cause the atom to have new properties such as being fissionable) uranium-235 or plutonuim-239. Then the nucleus splits into two halves. Each half of the nucleus has about the same amount of neutrons and protons. When the nucleus splits a great deal of thermal energy and gamma rays and two or more neutron are given off. Under some conditions those neutrons that were released come back and strike again. Then you two split halves of a nucleus. Then they give off the same thing and the neutrons come back and strike again, and again. This chain reaction results in which almost all the fissionable material is blown up. This cause the great explosion.
             All isotopes of uranium are fissionable, but uranium-235 is better than uranium-238 because it goes under fission quicker and gives off more neutrons per fission than Uranuim-238 or any other isotopes of uranium. plutonium-239 has the same characteristics of uranium-239. Both uranium-235 and plutonium-239 are used in the atomic bomb. If you use a small amount say .45 kg(1 lb) of uranium-235 or plutonium-239 it can't under go the chain reaction that is needed and is called subcritical. It can't undergo the chain reaction because the average of the neutrons released by the fission are likely not to hit another nucleus. Then if more of uranium-239 or plutonium-239 is added there is a higher percentage of neutrons hitting the nucleus. At the point when critical mass has been acomblished, and a chain reaction the explosion will be created.
             All subcritical fissionable material must be brought up to critical state extremely quick. One way to do that is to take two subcitical masses together at one point. When you combined those two subcritical masses you will achieve critical mass. How you do it is you use two high explosives to shoot the subcrital masses of fissionable material together in a hollow tube. The second way is to use an implosi...