/am'euh rish"ee euhm/, n. Chem.
a transuranic element, one of the products of high-energy helium bombardment of uranium and plutonium. Symbol: Am; at. no.: 95.
[1945-50, Amer.; AMERIC(A) + -IUM]

* * *

Synthetic radioactive chemical element, chemical symbol Am, atomic number 95.

The fourth transuranium element discovered, it was first produced in 1944 from plutonium-239 in a nuclear reactor. The isotope americium-241 has been prepared in kilogram quantities and is used in a variety of measuring applications that utilize its gamma radiation. Its most familiar use is in household smoke detectors.

* * *

 synthetic chemical element (atomic number 95) of the actinoid series of the periodic table. Undetected in nature, americium (as the isotope americium-241) was artificially produced from plutonium-239 (atomic number 94) in 1944 by Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso in a nuclear reactor. It was the fourth transuranium element to be discovered (curium, atomic number 96, was discovered a few months previously). The metal is silvery white and tarnishes slowly in dry air at room temperature. The isotope americium-241 is the most important because of its availability; it has been prepared in kilogram amounts from plutonium and has been used industrially in fluid-density gauges, thickness gauges, aircraft fuel gauges, and distance-sensing devices, all of which utilize its gamma radiation. The isotope's alpha-particle emission is exploited in smoke detectors. All isotopes of americium are radioactive; the stablest isotope, americium-243, has proved more convenient for chemical investigations in view of its longer half-life (7,370 years as compared with 458 years for americium-241).

      Americium reacts with oxygen to form the dioxide AmO2 and with hydrogen to form the hydride AmH2. There is some evidence that the ion Am2+ has been prepared in trace amounts, its existence suggesting that americium is similar to its lanthanoid homologue, europium, which can be reduced to its +2 oxidation state. Americium has four oxidation states, from +3 to +6, in acidic aqueous solution with the following ionic species: Am3+, pink; Am4+, rose (very unstable); AmO2 +, yellow; and AmO22+, light tan. In the common +3 state, americium is very similar to the other actinoid and lanthanoid elements.

atomic number
stablest isotope
melting point
above 850° C (1,550° F)
specific gravity
13.67 (20° C)
oxidation states
+2, +3, +4, +5, +6
electronic config.
[Rn]5f 77s2

* * *

Universalium. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Americium — Américium Américium Plutoni …   Wikipédia en Français

  • Américium — Plutonium ← Américium → Curium Eu …   Wikipédia en Français

  • AMÉRICIUM — L’américium (symbole Am) est un élément artificiel qui fait partie d’une série d’éléments lourds découverts depuis 1940, les transuraniens . Comme tous ces éléments, il possède de nombreux isotopes, tous radioactifs. Son numéro atomique, 95, le… …   Encyclopédie Universelle

  • Americium — (pronEng|ˌæməˈrɪsiəm) is a synthetic element that has the symbol Am and atomic number 95. A radioactive metallic element, americium is an actinide that was obtained in 1944 by bombarding plutonium with neutrons and was the fourth transuranic… …   Wikipedia

  • americium — AMERÍCIUM s.n. v. americiu. Trimis de ana zecheru, 13.09.2007. Sursa: DEX 98  AMERÍCIUM s.n. v. americiu. Trimis de LauraGellner, 13.09.2007. Sursa: DN …   Dicționar Român

  • americium — Symbol: Am Atomic number: 95 Atomic weight: (243) Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes. Am 243 is the most stable isotope, with a half life of 7.95*10^3 years. Discovered by Glenn T. Seaborg and… …   Elements of periodic system

  • americium — ☆ americium [am΄ər ish′ē əm, am΄əris′ē əm ] n. [ModL, after AMERIC(A) + IUM: so named by SEABORG Glenn T(heodore), one of its discoverers, by analogy with EUROPIUM, the corresponding rare earth] a radioactive, metallic chemical element, one of… …   English World dictionary

  • Americium — Eigenschaften …   Deutsch Wikipedia

  • Americium — Ame|ri|ci|um 〈n.; s; unz.; chem. 〉 künstlich hergestelltes radioaktives Element; oV Amerizium [nach Amerika] * * * A|me|ri|ci|um [engl. america = Amerika; ↑ ium (1)], das; s; Symbol: Am: nur künstlich herstellbares, radioaktives, metallisches… …   Universal-Lexikon

  • Americium — americis statusas T sritis fizika atitikmenys: angl. americium vok. Americium, n; Amerizium, n rus. америций, m pranc. américium, m …   Fizikos terminų žodynas

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”