Depends on what is in the atomic bomb. Most atomic bombs contain Uranium 235 and the half life of it is 703 Million years. So it would last a long time, this is due to the alpha particles produced from uranium.
The United States for the first time ever used the Atomic bomb on the Japanese cities of Hiroshima and Nagasaki. The effects of radiation on the population was to continue for many years.
The first atomic bomb used against mankind exploded at 8.15 over Hiroshima.
Harry Truman
US
The Battle of Okinawa did not lead to the atomic bomb, this battle happened in 1945 just a couple of months before the Manhattan Project completed the atomic bomb which they had been working on since 1942. With or without the Battle of Okinawa the atomic bomb would have been finished at the same time and dropped on Japan at the same time.
Japan
That city was destroyed by an atomic bomb on August 6 1945. It was the first time an atomic bomb was used against mankind.
never, but Leo Szilard who was working at Rutherford's lab at the time invented the atomic bomb in 1933.
about the time the manhattan project began in 1942, long before any existed.
11.45
heroshima