Back Amerikium AF አሜሪኪየም AM अमेरिशियम ANP أمريسيوم Arabic أميريكيوم ARY امريسيوم ARZ Americiu AST Amerisium AZ Amérisium BAN Амерыцый BE
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| Americium | ||||||||||||||||||||||||||||||||||
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| Pronunciation | /ˌæməˈrɪsiəm/ | |||||||||||||||||||||||||||||||||
| Appearance | silvery white | |||||||||||||||||||||||||||||||||
| Mass number | [243] | |||||||||||||||||||||||||||||||||
| Americium in the periodic table | ||||||||||||||||||||||||||||||||||
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| Atomic number (Z) | 95 | |||||||||||||||||||||||||||||||||
| Group | f-block groups (no number) | |||||||||||||||||||||||||||||||||
| Period | period 7 | |||||||||||||||||||||||||||||||||
| Block | f-block | |||||||||||||||||||||||||||||||||
| Electron configuration | [Rn] 5f7 7s2 | |||||||||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 32, 25, 8, 2 | |||||||||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||||||||
| Phase at STP | solid | |||||||||||||||||||||||||||||||||
| Melting point | 1449 K (1176 °C, 2149 °F) | |||||||||||||||||||||||||||||||||
| Boiling point | 2880 K (2607 °C, 4725 °F) (calculated) | |||||||||||||||||||||||||||||||||
| Density (near r.t.) | 12 g/cm3 | |||||||||||||||||||||||||||||||||
| Heat of fusion | 14.39 kJ/mol | |||||||||||||||||||||||||||||||||
| Molar heat capacity | 28[1] J/(mol·K) | |||||||||||||||||||||||||||||||||
Vapor pressure
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| Atomic properties | ||||||||||||||||||||||||||||||||||
| Oxidation states | common: +3 +2,[2] +4,[2] +5,[2] +6,[2] +7 | |||||||||||||||||||||||||||||||||
| Electronegativity | Pauling scale: 1.3 | |||||||||||||||||||||||||||||||||
| Ionization energies |
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| Atomic radius | empirical: 173 pm | |||||||||||||||||||||||||||||||||
| Covalent radius | 180±6 pm | |||||||||||||||||||||||||||||||||
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| Other properties | ||||||||||||||||||||||||||||||||||
| Natural occurrence | synthetic | |||||||||||||||||||||||||||||||||
| Crystal structure | double hexagonal close-packed (dhcp) | |||||||||||||||||||||||||||||||||
| Thermal conductivity | 10 W/(m⋅K) | |||||||||||||||||||||||||||||||||
| Electrical resistivity | 0.69 µΩ⋅m[1] | |||||||||||||||||||||||||||||||||
| Magnetic ordering | paramagnetic | |||||||||||||||||||||||||||||||||
| Molar magnetic susceptibility | +1000.0×10−6 cm3/mol[3] | |||||||||||||||||||||||||||||||||
| CAS Number | 7440-35-9 | |||||||||||||||||||||||||||||||||
| History | ||||||||||||||||||||||||||||||||||
| Naming | after the Americas | |||||||||||||||||||||||||||||||||
| Discovery | Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso (1944) | |||||||||||||||||||||||||||||||||
| Isotopes of americium | ||||||||||||||||||||||||||||||||||
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Americium is a synthetic chemical element; it has symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy.[5][6][7]
Americium was first produced in 1944 by the group of Glenn T. Seaborg from Berkeley, California, at the Metallurgical Laboratory of the University of Chicago, as part of the Manhattan Project. Although it is the third element in the transuranic series, it was discovered fourth, after the heavier curium. The discovery was kept secret and only released to the public in November 1945. Most americium is produced by uranium or plutonium being bombarded with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains about 100 grams of americium. It is widely used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Several unusual applications, such as nuclear batteries or fuel for space ships with nuclear propulsion, have been proposed for the isotope 242mAm, but they are as yet hindered by the scarcity and high price of this nuclear isomer.
Americium is a relatively soft radioactive metal with a silvery appearance. Its most common isotopes are 241Am and 243Am. In chemical compounds, americium usually assumes the oxidation state +3, especially in solutions. Several other oxidation states are known, ranging from +2 to +7, and can be identified by their characteristic optical absorption spectra. The crystal lattices of solid americium and its compounds contain small intrinsic radiogenic defects, due to metamictization induced by self-irradiation with alpha particles, which accumulates with time; this can cause a drift of some material properties over time, more noticeable in older samples.
- ^ a b Muller, W.; Schenkel, R.; Schmidt, H. E.; Spirlet, J. C.; McElroy, D. L.; Hall, R. O. A.; Mortimer, M. J. (1978). "The electrical resistivity and specific heat of americium metal". Journal of Low Temperature Physics. 30 (5–6): 561. Bibcode:1978JLTP...30..561M. doi:10.1007/BF00116197.
- ^ a b c d Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.
- ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
- ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
- ^ Seaborg, Glenn T. (1946). "The Transuranium Elements". Science. 104 (2704): 379–386. Bibcode:1946Sci...104..379S. doi:10.1126/science.104.2704.379. JSTOR 1675046. PMID 17842184.
- ^ Kostecka, Keith (2008). "Americium – From Discovery to the Smoke Detector and Beyond" (PDF). Bull. Hist. Chem. 33 (2): 89–93. Archived (PDF) from the original on 9 October 2022.
- ^ "C&En: It's Elemental: The Periodic Table - Americium".