Plutonium Radioactive Metal - Coursework Example

PLUTONIUM Name: (Insert name) Institution: (Insert Institution name) Lecturer: (Insert Lecturers name) Date: (Insert date) Plutonium is a radioactive metal, silver-white in colour. It is represented by the symbol Pu. It has an atomic number of 94. It was named after the planet Pluto by the persons who discovered it. Plutonium is considered one of the rare earth metals. In the periodic table, the rare earth metals are placed in the actinide and lanthanide series. Plutonium is an actinide (placed in the actinide series) placed in period 7 of the periodic table. The name actinide means artificial or synthetic. The elements on this series are manmade though plutonium occurs naturally in trace quantities in uranium ores. Plutonium is a radioactive metal. It emits radiation spontaneously and continuously. It is said to undergo radioactive decay. This is the spontaneous and continuous emission of radioactive particles, like alpha or beta particles, from the nucleus of the atom thus transforming the atom to another atom of lesser atomic mass and number. This process is called radioactive decaying (Rowland et al, 56). History and discovery of plutonium Plutonium was first produced in 14th December, 1940 by a man named Dr. Glenn Seaborg. He was a chemistry professor who was working at the University of Chicago in the metal laboratory at the time. He was working with other three men, Edwin McMillan, Arthur Wahl and Joseph Kennedy, when he discovered the element plutonium. Plutonium was artificially produced when they bombarded uranium with deuterons from a 60 inch cyclotron. This bombardment transmitted the uranium into plutonium. They named the element plutonium after the planet Pluto. They had earlier produced uranium and neptunium which were also named after the planets Uranus and Neptune in the order in which they were discovered (Seaborg, 34). Plutonium was artificially produced by bombarding a neutron with uranium. The uranium captures a neutron and undergoes some changes in its structure. It then emits beta particles. It was suspected that plutonium would undergo fission since it was initially from uranium which in earlier experiments, had exhibited these characteristics. The discoveries of these metals were kept as high profile secrets because of the world war that was going on. There were fears that the newly discovered elements could be used in the war. These fears came to pass during the bombing in Japan at Hiroshima and Nagasaki which was directly related to the three radioactive elements that had been discovered (Seaborg, 20). Physical and chemical properties of plutonium Plutonium is silvery white in colour though when exposed to air; it obtains a dark coating due to oxidation. Its atomic weight is 244 for the isotope with an atomic number 94. It is solid at room temperature. It melts at 913K and boils at 3501K. It has a density of 19.84 g/cm3. A piece of plutonium is warm due to the heat energy produced during the spontaneous alpha decay it goes through. Plutonium dissolves in hydrochloric acid forming the Pu+3 ion which is blue-purple in colour. Most of its reactions will form ligands with different ionic valence states. Other than the Pu+3, it has three other ionic valence states that are stable in aqueous solutions. They can be differentiated by the colours of the ligands. The Pu+4 has a yellow brown colour, the PuO+ is pink and the PuO+2 is pink orange in colour. PuO+ although formed is highly unstable in aqueous solutions. It dissociates into Pu+4 and PuO+2. The Pu+4 formed oxidizes the remaining PuO+ into PuO+2 and in this process, it is reduced to Pu+3. The final products of the dissociation therefore are Pu+3 and PuO+2.most reactions of plutonium take place in moist air forming oxides and halides. When plutonium reacts, its volume significantly increases up to about 70%. The product is usually a white flaky powder that ignites spontaneously (Audi et al, 76). Plutonium reacts with oxygen to form binary compounds plutonium oxide - PuO and plutonium dioxide -PuO2. It reacts with halides forming various products. It reacts with fluorine to form either PuF3 or PuF4. With chlorine, it forms PuCl3, with bromine PuBr3 and with iodine PuI3. The oxyhalides of plutonium are also known. These are PuOCl, PuOBr and PuOI. Plutonium reacts with carbon, nitrogen and silicon to form PuC, PuN and PuSi2 respectively. It also forms plutonium (II) hydride PuH2. Plutonium also reacts with selenium to form plutonium II selenide- PuSe, it reacts with sulphur giving Plutonium II sulphide PuS. It reacts with Nitrogen to give plutonium III nitride- PuN. Basically, plutonium has four major oxidation states and its compounds are in these states. The common oxidation states of plutonium are Pu+2, Pu+3, Pu+4 and Pu+6 (Rowland et al, 78). Due to the high radioactivity of plutonium, it is handled with a lot of care while carrying out these reactions in the laboratory. The alpha particles it produces while decaying are absorbed by the human bone marrow and could bring about adverse health problems. Radioactivity of plutonium Plutonium is a radioactive metal. This means that it constantly and spontaneously emits radioactive particles thus the original atom becomes another atom with a different mass number. When undergoing radioactive decay, an atom splits into two smaller atoms of lesser atomic numbers and masses. The by-product of this split is a radioactive particle like an alpha particle or a beta particle. A large amount of heat is also produced during this decay. A binary fission is where the atom divides into two particles. There are other instances where an atom splits into three other particles. This is called a tertiary fission. Plutonium undergoes alpha decay. This means that it emits alpha particles from its nucleus. Some of its isotopes however undergo beta decay (emit beta particles). The amount of time taken by an atom for it to radioactively split into two other atoms is called the half life of the atom. The half lives of each of the isotopes of plutonium vary. They are usually in years. The longest half life of a plutonium isotope is 80 million years. A small sample of plutonium for example will feel warm to the touch. A larger sample will boil water successively (Audi et al, 59). Plutonium is highly fissile. This means that is responds to being bombarded with a radioactive particle resulting in the formation of another particle. During the bombardment of a fissile atom, the nucleus of the atom breaks apart when struck with a neutron. Through fission, plutonium was formed by the bombardment of uranium with a neutron. Only three isotopes of plutonium are fissile; plutonium-239, plutonium-240 and plutonium-241. This radioactivity exhibited by plutonium is the reason for their use in weapons (explosive bombs). Isotopes of plutonium Plutonium has a total if fifteen isotopes. They are all radioactive but have different half lives. They are unstable due to their radioactivity. They do not stay in their state but decay emitting radioactive particles constantly therefore constantly changing. Therefore, the atomic masses of the isotopes of plutonium cannot be accurately measured. Their different half lives give them different properties and uses (Rowland et al, 120). Plutonium-238 with a half life of 87 years undergoes alpha decay. it is used in thermoelectric generators which are used in the generation of power for some space crafts. Plutonium-239 is considered the most important isotope of plutonium. It has a half life of 24 thousand years. It can sustain a nuclear chain reaction since it is highly fissile. It is commonly used in the making of nuclear weapons and nuclear reactors. Plutonium- 240 is not fissile but is fertile for fission. The most stable isotope of plutonium is plutonium-244 with a half life of 80 million years. This is the only isotope of plutonium four occurring naturally in uranium ores even though it is in trace amounts. Most plutonium isotopes decay very fast therefore they have not been studied conclusively. Uses of plutonium The uses of plutonium vary depending on the isotope in question since every isotope has a different half life. Plutonium-239 is used as a nuclear fuel in nuclear reactors. It is also used as a fuel in the fission of nuclear weapons. Plutonium-241 has a higher thermal neutron cross as compared with Plutonium-239. It is therefore difficult to use in thermal reactors. Plutonium is also used as a mixed oxide fuel. This is obtained from the already used plutonium in the nuclear fuel of light water reactors. It is usually a mixture of several plutonium isotopes mainly Pu-242, 239, 238 and 242. The mixture is not rich enough to power nuclear weapons but it is successively used as an oxide fuel. Plutonium is also used as a power and heat source. Pu-238 with a half life of 87 years produces a lot of heat during its fission. One kilogram of this isotope produces up to 570watts of energy in the form of heat energy. It is used to power spacecraft. It is also used to supply heat to scuba divers while under water (Rowland et al, 136). Works cited Audi, Wapstra, Thibault, Blachot and Bersillon. Plutonium. New York, 2003. Rowland, Keane and Lucas. Radioactive Plutonium. AEC Symp Series, 1973. Seaborg, Glenn. Radiobiology of Plutonium. Edited by Stover, B. J. and Jee, W. S. S., 1972. Read More