Atomic bomb

An atomic bomb is the name given to a device designed to produce an enormous explosion by harnessing nuclear energy.

The United States was the first nation to produce atomic bombs. So far, two bombs the United States dropped on the Japanese cities of Hiroshima and Nagasaki, in the closing days of World War 2, have been the only military uses of atomic weapons.

The first atomic bombs, like the two dropped on Japan, relied on producing a chain reaction of fissioning radioactive nuclei. Atoms of the heaviest elements found in nature, like Uranium and Thorium, have no stable isotopes. All isotopes are radioactive.