“americium”的意思、由来-百科全书

americium

chemical element

(Am),

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

243

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

词条	americium
释义	americium chemical element (Am), 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 95 stablest isotope 243 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
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