Why were the elements uranium and plutonium used in the atomic bombs of the Manhattan Project?
Uranium 235 and Plutonium 239 are both fissionable isotopes. This means that they undergo fission when they absorb a neutron, splitting into two lighter elements and releasing enormousl amounts of energy (as well as spitting out some neutrons – which can sustain a chain reaction if conditions are right). U-235 is obtained by separation from nautural uranium which contain only 0.07% U-235. Pu-239 is obtained from a nuclear reactor whereby U238 (the major isotope of natural uranium) adds a neutron to its nucleus and undergoes a transformation to neptunium-239 which splits off to become Pu-239.
