The year was 1919. The British physicist Lord Rutherford, who first theorized the existence of the atomic nucleus, bombards nitrogen-14 with alpha rays. The results are astounding. Rutherford finds that he has produced oxygen-17, a nonradioactive isotope of oxygen.
4/2He + 14/7N 17/8O + 1/1H
The dreams of the alchemists have come true! Rutherford, by having triggered the first humanly produced nuclear reaction, has "transmuted" an element.
The year is 1934. The French physicists Irene-Joliot-Curie and Frederick Joliot-Curie (daughter and son-in-law of Marie and Pierre Curie) bombard boron-10 with alpha rays and obtain nitrogen-13, the first artificially produced radioactive isotope.
10/5B + 4/2He 13/7N + 1/0n
You can see that by the 1930's scientists were unraveling the atom's secrets, and were about to discover the power of the atom. They were, in fact, on the verge of producing a nuclear chain reaction, which would turn very small quantities of mass into huge quantities of energy.
In 1934, the Italian physicist Enrico Fermi (who won the Nobel Prize in 1938) bombarded uranium (element 92) with neutrons in an attempt to produce element 93 (neptunium). But, instead, Fermi found himself with an isotope of barium (element 56), a mysterious outcome.
In 1938, the German physicist Otto Hahn, who was also working on atomic power proposed an explanation. He said that uranium atoms split into different atoms when they are bombarded with neutrons. (This splitting process is called nuclear fission.) Furthermore, when these uranium atoms split, they produce more neutrons, which in turn are able to split still more uranium atoms. This is called a branching chain reaction. You can liken it to placing dominoes in a triangular pattern. When you tip the first domino, it causes two others to tip over, and so on down the line.
In September 1939, Europe exploded into World War II, and many nations looked to their scientists for new weapons. Scientists all over the world who were working in the field of radioactivity knew that nuclear fission could be turned into a decisive weapon of war. It was only a matter of time before someone perfected the technique. Would the Germans be first? Were they racing toward that goal? (Fortunately for the free world, Hitler decided to turn the work of his nuclear scientists in other directions. This prevented the Germans from developing the atomic bomb prior to our doing so.) Everyone knew that their scientists were second to none.
The United States, although not yet at war, recognized the danger and launched a research program to produce an atomic (fission) bomb. Under Enrico Fermi's leadership, the Manhattan Project (code name) was started; it operated out of a windy, makeshift laboratory underneath the bleachers of Stagg Field on the University of Chicago. On December 2, 1942, Enrico Fermi and his team achieved the first sustained nuclear chain reaction. By July 1945, by incredible hard work and perseverance, the Manhattan Project scientists had managed to scrape together enough uranium-235 to make a fission bomb. To test it the United States had to fire it, and the first explosion of an A-bomb took place in a deserted area near Alamorgordo, New Mexico. It created great devastation which resulted in the construction of two more atomic bombs. The major reaction produced by the exploding A-bomb may be presented as:
235/92U + 1/0n 141/56Ba + 92/36Kr + 3 1/0n + energy
By August 1945 the other two bombs were ready. Yet such was the crisis-with Americans believing that they would lose a million American soldiers if they attempted to storm the Japanese mainland-that the United States went ahead and exploded them: the first at Hiroshima, and the second, for days later, at Nagasaki, Japan. Many Japanese people who lived in or near those two cities developed cancer as a result of their exposure to the radiation.