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: a bomb that produces an extremely powerful explosion when atoms are split apart
Full Definition of ATOMIC BOMB
: a bomb whose violent explosive power is due to the sudden release of energy resulting from the splitting of nuclei of a heavy chemical element (as plutonium or uranium) by neutrons in a very rapid chain reaction —called also atom bomb
First atomic bomb test, near Alamogordo, New Mexico, July 16, 1945.—Courtesy of Los Alamos National Laboratory, New Mexico
Weapon whose great explosive power results from the sudden release of energy upon the splitting, or fission, of the nuclei of heavy elements such as plutonium or uranium (seenuclear fission). With only 11–33 lb (5–15 kg) of highly enriched uranium, a modern atomic bomb could generate a 15-kiloton explosion, creating a huge fireball, a large shock wave, and lethal radioactive fallout. The first atomic bomb, developed by the Manhattan Project during World War II, was set off on July 16, 1945, in the New Mexico desert. The only atomic bombs used in war were dropped by the U.S. on Hiroshima on Aug. 6, 1945, and on Nagasaki three days later. In 1949 the Soviet Union tested its first atomic bomb, followed by Britain (1952), France (1960), China (1964), India (1974), and Pakistan (1998). Israel and South Africa were suspected of testing atomic weapons in 1979. See alsohydrogen bomb; Nuclear Non-proliferation Treaty; nuclear weapon.