Americium is a synthetic transuranic element produced in 1944 by group of Glenn. T Seaborg. It is present in spent nuclear fuel and should be neutralized because of its high radioactivity.
History and Discovery
Americium is a synthetic element which was produced in 1944 at Metallurgical Laboratory of University of Chicago, Berkeley. It was produced by group of Glenn. T Seaborg as a part of Manhattan Project. Element 95, Americium, was discovered later after the discovery of the element 96 of periodic table. Due to World War II the discovery of the new element was not disclosed until after the war. It was publicly announced in November 1945 . The element was named americium after Americas following the naming of the element above americium which is europium (belonging to lanthanide series) named after Europe.
|Periodic Table Classification||Group n/a
|State at 20C||Solid|
|Electron Configuration||[Rn] 5f7 7s2
|Electron Shell||2, 8, 18, 32, 25, 8, 2
|Density||13.67 g.cm-3 at 20°C|
|Atomic Mass||243.00 g.mol -1|
|Electronegativity according to Pauling||1.3|
Due to its relatively short half-life, by now any primordial americium would have been decayed. Americium is found in concentrated form on earth at the sites of nuclear weapons tests and at nuclear incidents sites. For research purposes it is produced artificially in small quantities. Americium is widely spread in atmosphere and soil where nuclear weapons sites, for instance, at Chernobyl disaster, desert floor in New Mexico where trinity nuclear bomb was tested and in Greenland where US bomber aircraft was crashed. Americium is also present in spent nuclear fuel.
Americium appears silvery white in colour. It has metallic lustre which tarnishes when exposed to air. It is a relatively soft element. It is a transuranic element and is highly radioactive. It is less dense than its immediate neighbouring elements. It has a high melting point, 1173 degree centigrade, higher than that of plutonium. It has low bulk modulus and can be easily deformed compared to the actinide elements before it. It belongs to actinide series and has atomic number 95. It is represented by symbol Am.
Americium is a reactive metal. Americium has chemical similarity to elements in lanthanide series. Americium readily dissolves in acids. It also reacts with oxygen forming americium oxide with oxidation states of +2, +3 and +4 . Americium reacts with halogens to form halides with +3 the most stable oxidation state. Americium also reacts with sulphur, telluride, antimony and bismuth. Various organometallic compounds of americium are also present.
Significance and Uses
- Americium is widely used to make smoke detectors for household and commercial purposes .
- Americium is used for thermo electric generators in space crafts.
- Americium-241 is used as source of alpha particle and gamma rays for various industrial and medical uses, for instance, for the diagnosis of thyroid function.
Americium is a toxic metal. Due to high radioactivity americium requires special precautions while handling. The gamma rays and neutrons emitted by various isotopes of americium can penetrate through thin storage material and can cause cellular damage in humans. If ingested americium can be deposited in the liver, bones and blood and only 10 per cent of it is excreted. The biological half-life of americium-241 in liver is around 20 years while in the bones it can be retained up to fifty years. Its high radioactivity has been linked to various cancers and because of this americium should be neutralized from the waste of nuclear power reactors before its disposal or the sites will have radiations that would be dangerous for human health . It is not a biologically important element.
Isotopes of Americium
There are 19 isotopes of americium. Americium-241 and americium-243 are the most abundantly occurring isotopes of americium. Americium-241 has a half-life of 432.2 years while americium-243 has a half-life of 7370 years and is the isotope of americium which has the longest half-life. They decay by alpha emission.
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