Americium

is a transuranic radioactive chemical element that has the symbol Am and atomic number 95. This transuranic element of the actinide series is located in the periodic table below the lantharide element europium, and thus by analogy was named after another continent, America.[|[2]] Americium was first produced in 1944 by the group of [|Glenn T. Seaborg] at the [|University of California, Berkeley]. 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 bombarding uranium or plutonium with alpha particles 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 a nuclear battery 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 silvery appearance. Its most common isotopes are 241Am and 243Am. In chemical compounds, they usually assume the oxidation state +3, especially in solutions. Several other oxidation states are known, which range from +2 to +7 and can be identified by their characteristic optical absorbtion spectra. The crystal lattice of solid americium and its compounds contains intrinsic defects, which are induced by self-irradiation with alpha particles and accumulate with time; this results in a drift of some material properties.
 * Americium**
 * Name:** Americium
 * Symbol:** Am
 * Atomic Number:** 95
 * Atomic Mass:** (243.0) amu
 * Boiling Point:** 2607.0 °C (2880.15 K, 4724.6 °F)[[image:imgres.jpeg width="227" height="345" align="right"]]
 * Number of Protons/Electrons:** 95
 * Number of Neutrons:** 148
 * Classification:** Rare Earth
 * Crystal Structure:** Hexagonal
 * Density @ 293 K:** 13.6 g/cm 3
 * Color:** Unknown

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0095.gif width="383" height="381"]] ||  || **Number of Energy Levels:** 7
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** **Fifth Energy Level:** **Sixth Energy Level:** **Seventh Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Am-240 || 2.1 days ||
 * Am-241 || 432.7 years ||
 * Am-242 || 16.0 hours ||
 * Am-242m || 141.0 years ||
 * Am-243 || 7370.0 years ||
 * Am-244 || 10.1 hours ||
 * Am-245 || 2.1 hours ||
 * Am-246 || 39.0 minutes ||

Facts
Uses**:** Smoke Detectors
 * Date of Discovery:** 1945
 * Discoverer:** G.T. Seaborg
 * Name Origin:** After America
 * Obtained From:** Man-made

What's in a name? Named for the Americas. Say what? Americium is pronounced as am-er-ISH-ee-em. History and Uses: Americium was discovered in 1944 by the American scientists Glenn T. Seaborg, Ralph A. James, Leon O. Morgan and Albert Ghiorso. They produced americium by bombarding plutonium-239, an isotope of plutonium, with high energy neutrons. This formed plutonium-240, which was itself bombarded with neutrons. The plutonium-240 changed into plutonium-241, which then decayed into americium-241 through beta decay. This work was carried out at the University of Chicago's Metallurgical Laboratory, now known as Argonne National Laboratory. Americium's most stable isotope, americium-243, has a half-life of about 7,370 years. It decays into neptunium-239 through alpha decay. Americium can be produced in kilogram quantities and has a few practical uses. It is used in smoke detectors and can be used as a portable source of gamma rays. Americium-241, with a half-life of 432.2 years, is used in these products because it is easier to produce relatively pure samples of this isotope. Estimated Crustal Abundance: Not Applicable Estimated Oceanic Abundance: Not Applicable Number of Stable Isotopes: 0 (View all isotope data) Ionization Energy: 5.993 eV Oxidation States: +6, +5, +4, +3

In the periodic table, americium is located right to plutonium, left to curium, and below the lanthanide europium, with which it shares many similarities in physical and chemical properties. Americium is a highly radioactive element. When freshly prepared, it has a silvery-white metallic lustre, but then slowly tarnishes in air. With a density of 12 g/cm3, americium is lighter than both curium (13.52 g/cm3) and plutonium (19.8 g/cm3); but is heavier than europium (5.264 g/cm3)—mostly because of its higher atomic mass. Americium is relatively soft and easily deformable and has a significantly lower bulk modulus than the actinides before it: Th, Pa, U, Np and Pu.[39home] Its melting point of 1173 °C is significantly higher than that of plutonium (639 °C) and europium (826 °C), but lower than for curium (1340 °C).[38home][38home][40home] At ambient conditions, americium is present in its most stable α form which has a hexagonal crystal symmetry, and a space group P63/mmc with lattice parameters //a// = 346.8 pm and //c// = 1124 pm, and four atoms per unit cell. The crystal consists of a double-hexagonal close packing with the layer sequence ABAC and so is isotypic with α-lanthanum and several actinides such as α-curium.[36home][40home] The crystal structure of americium changes with pressure and temperature. When compressed at room temperature to 5 GPa, α-Am transforms to the β modification, which has a face-centered cubic (//fcc//) symmetry, space group Fm 3 m and lattice constant //a// = 489 pm. This //fcc// structure is equivalent to the closest packing with the sequence ABC.[36home][40home] Upon further compression to 23 GPa, americium transforms to an orthorhombic γ-Am structure similar to that of α-uranium. There are no further transitions observed up to 52 GPa, except for an appearance of a monoclinic phase at pressures between 10 and 15 GPa.[39home] There is no consistency on the status of this phase in the literature, which also sometimes lists the α, β and γ phases as I, II and III. The β-γ transition is accompanied by a 6% decrease in the crystal volume; although theory also predicts a significant volume change for the α-β transition, it is not observed experimentally. The pressure of the α-β transition decreases with increasing temperature, and when α-americium is heated at ambient pressure, at 770 °C it changes into an //fcc// phase which is different from β-Am, and at 1075 °C it converts to a body-centered cubic structure. The pressure-temperature phase diagram of americium is thus rather