Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Plutonium is a transuranic radioactive chemical element with the symbol Pu and atomic number 94. Plutonium is the heaviest primordial element by virtue of its most stable isotope, plutonium-244, whose half-life of about 80 million years is just long enough for the element to be found in trace quantities in nature. Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II, which developed the first atomic bombs. The first nuclear test, "Trinity" (July 1945), and the second atomic bomb used to destroy a city, "Fat Man", both had cores of plutonium-239. Learn more about plutonium, its isotopes and alloys and their applications in this book.