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Americium

(243)

Name: Americium
Symbol: Am
Atomic number: 95
Atomic weight: (243)
CAS Registry ID: 7440-35-9

Group name: Actinoid
Period number: 7
Block: f-block
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Description

Americium is an actinide that has a silvery white, or yellow, color in its natural solid state. It tarnishes in dry air, and it is somewhat malleable. Americium has an atomic weight of 243, a melting point of 2149 °F, and a boiling point of 4725 °F. Americium does not have many commercial uses as it is very expensive to produce. Americium is used in minute quantities in some smoke detectors, in the production of certain types of glasses, and as a source of ionizing radiation.

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Isolation

Americium is not found freely in nature, and it must be synthesized for its commercial and laboratory uses; isolation procedures of this element are still being studied.

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Americium is synthesized using the bombardment of plutonium with neutrons. The process begins with the donation of neutrons that are created either through nuclear fission, nuclear fusion, or through high energy reactions. The bombardment of neutrons on the plutonium causes the plutonium to absorb the extra neutrons which forms the element americium. Neutron bombardment takes place in specialized containers as this process causes dislocations in metals; metals that are exposed to neutron bombardment become brittle, and some metals even begin to swell. There are current studies on the solvent extraction possibilities of americium; these studies may result in reduced toxic wastes that are produced by nuclear reactors. By removing americium through liquid to liquid extractions, it may be possible to remove radioactive elements in the nuclear wastes that have long half lives. America is a synthetic element, and it can only be created and extracted through very specialized methods.

General
Name	Americium
Symbol	Am
Number	95
Chemical series	actinides
Group	n/a
Period	7
Block	f
Appearance	silvery white
Standard atomic weight	(243) g·mol⁻¹
Electron configuration	[Rn] 5f⁷ 7s²
Electrons per shell	2, 8, 18, 32, 25, 8, 2

Atomic properties
Crystal structure	hexagonal
Oxidation states	6, 5, 4, 3 (amphoteric oxide)
Electronegativity	1.3 (scale Pauling)
Ionization energies	1st: 578 kJ/mol
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Atomic radius	175 pm
Atomic radius (calc.)
Covalent radius
Van der Waals radius

Physical properties
Phase	solid
Density (near r.t.)	12 g·cm⁻³
Liquid density at m.p.
Melting point	1449 K (1176 °C, 2149 °F)
Boiling point	2880 K (2607 °C, 4725 °F)
Critical point
Heat of fusion	14.39 kJ·mol⁻¹
Heat of vaporization
Heat capacity	(25 °C) 62.7 J·mol⁻¹·K⁻¹

Miscellaneous
Magnetic ordering
Electrical resistivity
Thermal conductivity	(300 K) 10 W·m⁻¹·K⁻¹
Thermal expansion
Speed of sound (thin rod)
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness
CAS registry number	7440-35-9

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Americium

Description

Isolation

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