Uranium
Uranium is a dull gray metallic element with a melting point of 1135°C (2075°F) and a boiling point of 4134°C (7473°F). It is relatively abundant in Earth's crust, ranking number 47 among the elements. Although perhaps not as well known, it is actually more abundant than more familiar elements such as tin, silver, mercury and gold. Natural uranium consists of three isotopes of mass numbers 234 (0.005 percent), 235 (0.711 percent) and 238 (99.283 percent). All three isotopes are radioactive.
Radio activity of uranium
Properties and Uses:
By far the most important property of uranium is its radioactivity. Its most abundant isotope, uranium–238, decays by emitting an alpha particle with a half–life of 4.47 × 109 years. (Recall that the half–life of a radioactive element is the time it takes for one–half of a given sample to decay). The half–life of uranium–238 is about equal to the age of Earth. That means that about one–half of all the uranium found on Earth at its moment of creation is still here. The other one–half has decayed to other elements.
Knowing the half life of uranium–238 (and many other radioactive isotopes) allows scientists to estimate the age of rocks. The amount of uranium–238 found in any particular rock is compared to the amount of daughter isotopes found with it. A daughter isotope is an isotope formed when some parent isotope, such as uranium–238, decays. The more daughter isotope present in a sample, the older the rock; the less daughter isotope, the younger the rock.
Uranium used in nuclear weapons
The second most abundant isotope of uranium, uranium–235, has the rare property of being fissionable, meaning that its atomic nuclei will break apart when bombarded by neutrons. The fission of a uranium–235 nucleus releases very large amounts of energy, additional neutrons and two large fission products. The fission products are the atomic nuclei formed when a fissionable nucleus such as uranium–235 breaks apart.
The fission of uranium–235 nuclei has become extremely important in the manufacture of nuclear weapons and in the operation of nuclear power plants. In fact, these applications account for the primary applications of uranium in everyday life.