americium C화학적 특성, 용도, 생산
화학적 성질
AMERICIUM, Chemical element, symbol Am, at no. 95, at. wt. 243 (mass number of the most stable isotope), radioactive metal of the actinide series, also one of the transuranium elements. All isotopes of americium are radioactive; all must be produced synthetically. The element was discovered by G.T. Seaborg and associates at the Metallurgical Laboratory of the University of Chicago in 1945. At that time, the element was obtained by bombarding uranium-238 with helium ions to produce
241Am, which has a half-life of 475 years. Subsequently,
241Am has been produced by bombardment of plutonium-241 with neutrons in a nuclear reactor. 243Am is the most stable isotope, an alpha emitter with a half-life of 7950 years. Other known isotopes are
237Am,
238 Am,
240 Am,
241Am,
242Am,
244 Am,
245 Am, and
246Am.
This element exists in acidic aqueous solution in the (III), (IV), (V), and (VI) oxidation states with the ionic species probably corresponding to Am3+, Am4+, AmO2 + and AmO2 2+. The colors of the ions are: Am3+, pink; Am4+, rose; AmO2 +, yellow; and AmO2 2+, rum-colored.
물리적 성질
All the isotopes of americium belonging to the transuranic subseries of the actinide seriesare radioactive and are artificially produced. Americium has similar chemical and physicalcharacteristics and is homologous to europium, located just above it in the rare-earth (lanthanide)series on the periodic table. It is a bright-white malleable heavy metal that is somewhatsimilar to lead. Americium’s melting point is 1,176°C, its boiling point is 2,607°C, and itsdensity is 13.68g/cm
3.
Isotopes
There are 24 isotopes of americium. All are radioactive with half-lives rangingfrom 72 microseconds to over 7,000 years. Five of americium’s isotopes are fissionablewith spontaneous alpha decay.
Origin of Name
Named after the continent America because Europium was named
after the European continent.
출처
Americium does not exist in nature. All of its isotopes are man-made and radioactive.Americium-241 is produced by bombarding plutonium-239 with high-energy neutrons,resulting in the isotope plutonium-240 that again is bombarded with neutrons and resultsin the formation of plutonium-241, which in turn finally decays into americium-241 by theprocess of beta decay. Both americium-241 and americium-243 are produced within nuclearreactors. The reaction is as follows:
239Pu + (neutron and λ gamma rays) →
240Pu + (neutronand λ gamma rays) →
241Pu→
241Am + beta minus (β-); followed by
241Am→
93Np-237 +
4He
2 (helium nuclei).
Characteristics
Although americium’s main valence (oxidation state) is +3, it is tetravalent. It can formcompounds with its ions of +4, +5, and +6, particularly when oxidized. Its most stable isotopeis americium-243, with a half-life of 7,379 years, which, over time through alpha decay,transmutates into neptunium-239.
용도
Gamma radiography, radiochemical research, diagnostic aid, electronic devices.
정의
Am. A synthetic radioactive element of atomic number 95, a member of the actinide series; aw 241; 14 isotopes of widely varying half-life; valence 3, but divalent, tetravalent, and higher valencies exist. α and γ emitter, forms compounds with oxygen, halides, lithium, etc. Metallic americium is silver-white crystalline, d 13.6, mp approximately 100C. Half-life of 241 Am is 458 years.
위험도
All the isotopes and compounds of americium are deadly sources of radiation and causeradiation poisoning and death. Precautions must be taken when working with it. The smallamount of americium-241 found in smoke detectors in household smoke alarms is harmlessunless the isotope is removed and swallowed.
americium 준비 용품 및 원자재
원자재
준비 용품
