The first challenge of the project was thus to determine the most efficient way to separate and purify uranium-235 from the overly-abundant uranium-238 - standard methods of separation could not be used due to the strong chemical similarity between the two isotopes. When a neutron bombards U-238, the isotope often captures the neutron to become U-239, failing to fission, and thus failing to instigate a chain reaction that would detonate a bomb. Most uranium found naturally in the world exists as uranium-238, leaving only 0.7% of naturally existing uranium as the U-235 isotope. Little Boy was powered by the uranium isotope U-235 in a process that didnвЂ™t come easily to the many Manhattan Project scientists working on the uranium extraction and enrichment process. Little Boy detonated due to a fission chain reaction involving the isotope U-235 of uranium, while Fat Man used plutoniumвЂ™s Pu-239 form. Little Boy and Fat Man utilized different elements and completely separate methods of construction in order to function as nuclear weapons. Critical mass is defined as the amount of material at which a neutron produced by a fission process will, on average, create another fission event. The more fissionable material you have, the greater the odds that such an event will occur. This means you need enough U-235 or Pu-239 to ensure that neutrons released by fission will strike another nucleus, thus producing a chain reaction. In order to detonate an atomic weapon, you need a critical mass of fissionable material. For more on this topic, see Nuclear Fission. Both of those neutrons collide with uranium-235 atoms, each of which fission and release between one and three neutrons, and so on. However, one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and some binding energy. Two neutrons do not continue the reaction because they are lost or absorbed by a uranium-238 atom. When a uranium-235 atom absorbs a neutron and fissions into two new atoms, it releases three new neutrons and some binding energy.

This is known as a chain reaction and is what causes an atomic explosion. The fission process becomes self-sustaining as neutrons produced by the splitting of atom strike nearby nuclei and produce more fission. Fission occurs when a neutron strikes the nucleus of either isotope, splitting the nucleus into fragments and releasing a tremendous amount of energy. The isotopes uranium-235 and plutonium-239 were selected by the atomic scientists because they readily undergo fission. The second weapon, dropped on Nagasaki, was called Fat Man and was an implosion-type device with a plutonium core. The first, Little Boy, was a gun-type weapon with a uranium core. developed two types of atomic bombs during the Second World War. Really, does this childish drek have to appear in EVERY conversation here? WE KNOW that unlike America or Britain, the dominant psychopaths of Japan at that time did horrendous deeds like trying to WIPE OUT an entire continent of Native Peoples.oh wait.um.like doing what they emerged from 'isolation' observing Europeans and Americans doing with great enthusiasm and emulating them but never even approaching the body count which the WORST of the Europeans achieved all over this planet and bragged that the Sun never set upon their sins.The immense destructive power of atomic weapons derives from a sudden release of energy produced by splitting the nuclei of the fissile elements making up the bombs' core. What did the author of that statement expect the US to do? It also conveniently ignores the reason the US entered that war, a Japanese attack on Hawaii followed immediately with attacks on Philippines and Guam. Thank you.ДЄnd the author of that statement probably doesn't even realize that could be a very accurate description of what the IJA did to many cities in China, down the length of Asia to Singapore. Sorry for confusedly adding misinformation but that's what science does, backs itself up and corrects the errors that inadvertently occur.

James Maxwell, the Scottish scientist, not Robert Maxwell the English MP crook and spy.ДЄh yes, Jonathan, the head gets a little bollixed late at night.

Atomic science 1.7.10