Electrons: 92neutrons: 143
protons: 92.
One of the radioactive elements used for nuclear energy is 235U92, commonly stated as U-235.
Uranium ore is a heterogeneous mixture
Nuclear energy was used in World War II to detonate two nuclear warheads over Hiroshima, Japan, on August 6, 1945, and over Nagasaki, on August 9, 1945.The Hiroshima weapon was comprised of two subcritical mases of 235U92, that were driven into each other by conventional explosives, going super prompt critical and exploding.The Nagasaki weapon was comprised of a sphere of 239Pu94 surrounding a polonium/beryllium neutron initiator, all surrounded by shaped charges of convertional explosives. The same mechanism applies on detonation.Some sources state a different configuration, in that the Hiroshima weapon was actually 239Pu94 , while the Nagasaki weapon was actually 235U92, surrounded by layers of Beryllium. The opposite seems more correct, from a physics standpoint, so this is either a misunderstanding by this auther, a mistatement by some older documents, or by mis-information. Any one with better knowledge is, of course, welcom to refine this answer.
A half life pertains to the time it takes for exactly half of a substance to disappear. So, if U235 has a half life of 700 million years, it will take 700 million years for half of it to decay. That would leave .5kg or 500g.