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Actinium | Chemical compounds | Chemical compounds
Due to actinium's intense radioactivity, only a limited number of actinium compounds are known. These include: AcF3, AcCl3, AcBr3, AcOF, AcOCl, AcOBr, Ac2S3, Ac2O3, AcPO4 and Ac(NO3)3. They all contain actinium in the oxidation state +3. In particular, the lattice constants of the analogous lanthanu... |
Actinium | Oxides | Oxides
Actinium oxide (Ac2O3) can be obtained by heating the hydroxide at or the oxalate at , in vacuum. Its crystal lattice is isotypic with the oxides of most trivalent rare-earth metals. |
Actinium | Halides | Halides
Actinium trifluoride can be produced either in solution or in solid reaction. The former reaction is carried out at room temperature, by adding hydrofluoric acid to a solution containing actinium ions. In the latter method, actinium metal is treated with hydrogen fluoride vapors at in an all-platinum setup. Tr... |
Actinium | Other compounds | Other compounds
Actinium hydride was obtained by reduction of actinium trichloride with potassium at , and its structure was deduced by analogy with the corresponding LaH2 hydride. The source of hydrogen in the reaction was uncertain.Meyer, p. 43
Mixing monosodium phosphate (NaH2PO4) with a solution of actinium in hyd... |
Actinium | Isotopes | Isotopes
Naturally occurring actinium is principally composed of two radioactive isotopes; (from the radioactive family of ) and (a granddaughter of ). decays mainly as a beta emitter with a very small energy, but in 1.38% of cases it emits an alpha particle, so it can readily be identified through alpha spectromet... |
Actinium | Occurrence and synthesis | Occurrence and synthesis
upright=0.70|thumb|Uraninite ores have elevated concentrations of actinium.
Actinium is found only in traces in uranium ores – one tonne of uranium in ore contains about 0.2 milligrams of 227Ac – and in thorium ores, which contain about 5 nanograms of 228Ac per one tonne of thorium. The actiniu... |
Actinium | Applications | Applications
Owing to its scarcity, high price and radioactivity, 227Ac currently has no significant industrial use, but 225Ac is currently being studied for use in cancer treatments such as targeted alpha therapies.
227Ac is highly radioactive and was therefore studied for use as an active element of radioisotope ther... |
Actinium | Precautions | Precautions
227Ac is highly radioactive and experiments with it are carried out in a specially designed laboratory equipped with a tight glove box. When actinium trichloride is administered intravenously to rats, about 33% of actinium is deposited into the bones and 50% into the liver. Its toxicity is comparable to, bu... |
Actinium | See also | See also
Actinium series |
Actinium | Notes | Notes |
Actinium | References | References |
Actinium | Bibliography | Bibliography
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Actinium | External links | External links
Actinium at The Periodic Table of Videos (University of Nottingham)
NLM Hazardous Substances Databank – Actinium, Radioactive
Actinium in
Category:Chemical elements
Category:Chemical elements with face-centered cubic structure
Category:Actinides |
Actinium | Table of Content | Distinguish, History, Properties, Chemical compounds, Oxides, Halides, Other compounds, Isotopes, Occurrence and synthesis, Applications, Precautions, See also, Notes, References, Bibliography, External links |
Americium | good article | 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.
Americium was first produced in 1944 by the group of... |
Americium | History | History
thumb|left|The 60-inch cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley, in August 1939
Although americium was likely produced in previous nuclear experiments, it was first intentionally synthesized, isolated and identified in late autumn 1944, at the University of California,... |
Americium | Occurrence | Occurrence
thumb|Americium was detected in the fallout from the Ivy Mike nuclear test.
The longest-lived and most common isotopes of americium, 241Am and 243Am, have half-lives of 432.2 and 7,370 years, respectively. Therefore, any primordial americium (americium that was present on Earth during its formation) should ... |
Americium | Synthesis and extraction | Synthesis and extraction |
Americium | Isotope nucleosynthesis | Isotope nucleosynthesis
thumb|Chromatographic elution curves revealing the similarity between the lanthanides Tb, Gd, and Eu and the corresponding actinides Bk, Cm, and Am
Americium has been produced in small quantities in nuclear reactors for decades, and kilograms of its 241Am and 243Am isotopes have been accumulate... |
Americium | Metal generation | Metal generation
Most synthesis routines yield a mixture of different actinide isotopes in oxide forms, from which isotopes of americium can be separated. In a typical procedure, the spent reactor fuel (e.g. MOX fuel) is dissolved in nitric acid, and the bulk of uranium and plutonium is removed using a PUREX-type ext... |
Americium | Physical properties | Physical properties
thumb|Double-hexagonal close packing with the layer sequence ABAC in the crystal structure of α-americium (A: green, B: blue, C: red)
In the periodic table, americium is located to the right of plutonium, to the left of curium, and below the lanthanide europium, with which it shares many physical a... |
Americium | Chemical properties | Chemical properties
Americium metal readily reacts with oxygen and dissolves in aqueous acids. The most stable oxidation state for americium is +3.Penneman, p. 4 The chemistry of americium(III) has many similarities to the chemistry of lanthanide(III) compounds. For example, trivalent americium forms insoluble fluoride... |
Americium | Chemical compounds | Chemical compounds |
Americium | Oxygen compounds | Oxygen compounds
Three americium oxides are known, with the oxidation states +2 (AmO), +3 (Am2O3) and +4 (AmO2). Americium(II) oxide was prepared in minute amounts and has not been characterized in detail. Americium(III) oxide is a red-brown solid with a melting point of 2205 °C.Wiberg, p. 1972 Americium(IV) oxide is t... |
Americium | Halides | Halides
Halides of americium are known for the oxidation states +2, +3 and +4,Wiberg, p. 1969 where the +3 is most stable, especially in solutions.
Oxidation state F Cl Br I +4 Americium(IV) fluoride AmF4 pale pink +3 Americium(III) fluoride AmF3 pink Americium(III) chloride AmCl3 pink Americium(III) bromide AmBr... |
Americium | Chalcogenides and pnictides | Chalcogenides and pnictides
The known chalcogenides of americium include the sulfide AmS2, selenides AmSe2 and Am3Se4, and tellurides Am2Te3 and AmTe2. The pnictides of americium (243Am) of the AmX type are known for the elements phosphorus, arsenic, antimony and bismuth. They crystallize in the rock-salt lattice. |
Americium | Silicides and borides | Silicides and borides
Americium monosilicide (AmSi) and "disilicide" (nominally AmSix with: 1.87 < x < 2.0) were obtained by reduction of americium(III) fluoride with elementary silicon in vacuum at 1050 °C (AmSi) and 1150−1200 °C (AmSix). AmSi is a black solid isomorphic with LaSi, it has an orthorhombic crystal symme... |
Americium | Organoamericium compounds | Organoamericium compounds
thumb|upright=0.55|Predicted structure of amerocene [(η8-C8H8)2Am]
Analogous to uranocene, americium is predicted to form the organometallic compound amerocene with two cyclooctatetraene ligands, with the chemical formula (η8-C8H8)2Am. A cyclopentadienyl complex is also known that is likely to... |
Americium | Biological aspects | Biological aspects
Americium is an artificial element of recent origin, and thus does not have a biological requirement.Toeniskoetter, Steve; Dommer, Jennifer and Dodge, Tony The Biochemical Periodic Tables – Americium, University of Minnesota, Retrieved 28 November 2010 It is harmful to life. It has been proposed to u... |
Americium | Fission | Fission
The isotope 242mAm (half-life 141 years) has the largest cross sections for absorption of thermal neutrons (5,700 barns),Pfennig, G.; Klewe-Nebenius, H and Seelmann Eggebert, W. (Eds.): Karlsruhe nuclide, 7 Edition 2006. that results in a small critical mass for a sustained nuclear chain reaction. The critical ... |
Americium | Isotopes | Isotopes
About 18 isotopes and 11 nuclear isomers are known for americium, having mass numbers 229, 230, and 232 through 247. There are two long-lived alpha-emitters; 243Am has a half-life of 7,370 years and is the most stable isotope, and 241Am has a half-life of 432.2 years. The most stable nuclear isomer is 242m1Am... |
Americium | Applications | Applications |
Americium | Ionization-type smoke detector | Ionization-type smoke detector
Americium is used in the most common type of household smoke detector, which uses 241Am in the form of americium dioxide as its source of ionizing radiation. This isotope is preferred over 226Ra because it emits 5 times more alpha particles and relatively little harmful gamma radiation.
... |
Americium | Radionuclide | Radionuclide
As 241Am has a roughly similar half-life to 238Pu (432.2 years vs. 87 years), it has been proposed as an active element of radioisotope thermoelectric generators, for example in spacecraft.Basic elements of static RTGs , G.L. Kulcinski, NEEP 602 Course Notes (Spring 2000), Nuclear Power in Space, Universit... |
Americium | Neutron source | Neutron source
The oxide of 241Am pressed with beryllium is an efficient neutron source. Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:
^{241}_{95}Am -> ^{237}_{93}Np + ^{4}_{2}He + \gamma
^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}... |
Americium | Production of other elements | Production of other elements
Americium is a starting material for the production of other transuranic elements and transactinides – for example, 82.7% of 242Am decays to 242Cm and 17.3% to 242Pu. In the nuclear reactor, 242Am is also up-converted by neutron capture to 243Am and 244Am, which transforms by β-decay to 244... |
Americium | Spectrometer | Spectrometer
Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. The 59.5409 keV gamma ray emissions from 241Am in such sources can be used for indirect analysis of materials in radiography and X-ray fluorescence spectroscopy, as well as f... |
Americium | Health concerns | Health concerns
As a highly radioactive element, americium and its compounds must be handled only in an appropriate laboratory under special arrangements. Although most americium isotopes predominantly emit alpha particles which can be blocked by thin layers of common materials, many of the daughter products emit gamma... |
Americium | See also | See also
Actinides in the environment
:Category:Americium compounds |
Americium | Notes | Notes |
Americium | References | References |
Americium | Bibliography | Bibliography
Penneman, R. A. and Keenan T. K. The radiochemistry of americium and curium, University of California, Los Alamos, California, 1960
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Americium | Further reading | Further reading
Nuclides and Isotopes – 14th Edition, GE Nuclear Energy, 1989.
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Americium | External links | External links
Americium at The Periodic Table of Videos (University of Nottingham)
ATSDR – Public Health Statement: Americium
World Nuclear Association – Smoke Detectors and Americium
Category:Chemical elements
Category:Chemical elements with double hexagonal close-packed structure
Category:Actinides
Category:... |
Americium | Table of Content | good article, History, Occurrence, Synthesis and extraction, Isotope nucleosynthesis, Metal generation, Physical properties, Chemical properties, Chemical compounds, Oxygen compounds, Halides, Chalcogenides and pnictides, Silicides and borides, Organoamericium compounds, Biological aspects, Fission, Isotopes, Applicati... |
Astatine | Featured article | Astatine is a chemical element; it has symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Consequen... |
Astatine | Characteristics | Characteristics
Astatine is an extremely radioactive element; all its isotopes have half-lives of 8.1 hours or less, decaying into other astatine isotopes, bismuth, polonium, or radon. Most of its isotopes are very unstable, with half-lives of seconds or less. Of the first 101 elements in the periodic table, only fra... |
Astatine | Physical | Physical
Most of the physical properties of astatine have been estimated (by interpolation or extrapolation), using theoretically or empirically derived methods. For example, halogens get darker with increasing atomic weight – fluorine is nearly colorless, chlorine is yellow-green, bromine is red-brown, and iodine is... |
Astatine | Chemical | Chemical
The chemistry of astatine is "clouded by the extremely low concentrations at which astatine experiments have been conducted, and the possibility of reactions with impurities, walls and filters, or radioactivity by-products, and other unwanted nano-scale interactions". Many of its apparent chemical properties... |
Astatine | Compounds | Compounds
Less reactive than iodine, astatine is the least reactive of the halogens; the chemical properties of tennessine, the next-heavier group 17 element, have not yet been investigated, however. Astatine compounds have been synthesized in nano-scale amounts and studied as intensively as possible before their r... |
Astatine | History | History
In 1869, when Dmitri Mendeleev published his periodic table, the space under iodine was empty; after Niels Bohr established the physical basis of the classification of chemical elements, it was suggested that the fifth halogen belonged there. Before its officially recognized discovery, it was called "eka-iod... |
Astatine | Isotopes | Isotopes
+ Alpha decay characteristics for sample astatine isotopes Massnumber Half-life Probabilityof alphadecay Alpha-decayhalf-life 207 % 208 % 209 % 210 % 211 % 212 ≈100% 213 % 214 % 219 % 220 % 221 experimentallyalpha-stable ∞
There are 41 known isotopes of astatine, with mass numbers of 1... |
Astatine | Natural occurrence | Natural occurrence
thumb|upright=0.7|alt=a sequence of differently colored balls, each containing a two-letter symbol and some numbers|Neptunium series, showing the decay products, including astatine-217, formed from neptunium-237
Astatine is the rarest naturally occurring element. The total amount of astatine in th... |
Astatine | Synthesis | Synthesis |
Astatine | Formation | Formation
+ Possible reactions after bombarding bismuth-209 with alpha particles Reaction Energy of alpha particle Threshold energy Maximum production + → + 2 n 20.7 MeV 30–31 MeV + → + 3 n 28.4–28.6 MeV 37 MeV + → + 4 n 35.9 MeV
thumb|left|The bismuth target after irradiation contains minuscule quantities ... |
Astatine | Separation methods | Separation methods
Since astatine is the main product of the synthesis, after its formation it must only be separated from the target and any significant contaminants. Several methods are available, "but they generally follow one of two approaches—dry distillation or [wet] acid treatment of the target followed by sol... |
Astatine | Dry | Dry
The astatine-containing cyclotron target is heated to a temperature of around 650 °C. The astatine volatilizes and is condensed in (typically) a cold trap. Higher temperatures of up to around 850 °C may increase the yield, at the risk of bismuth contamination from concurrent volatilization. Redistilling the conde... |
Astatine | Wet | Wet
The irradiated bismuth (or sometimes bismuth trioxide) target is first dissolved in, for example, concentrated nitric or perchloric acid. Following this first step, the acid can be distilled away to leave behind a white residue that contains both bismuth and the desired astatine product. This residue is then diss... |
Astatine | Uses and precautions | Uses and precautions
+ Several 211At-containing molecules and their experimental uses Agent Applications [211At]astatine-tellurium colloids Compartmental tumors 6-[211At]astato-2-methyl-1,4-naphtaquinol diphosphate Adenocarcinomas 211At-labeled methylene blue Melanomas Meta-[211At]astatobenzyl guanidine Neuroendocrin... |
Astatine | See also | See also
Radiation protection |
Astatine | Notes | Notes |
Astatine | References | References |
Astatine | Bibliography | Bibliography
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Astatine | External links | External links
Astatine at The Periodic Table of Videos (University of Nottingham)
Astatine: Halogen or Metal?
Category:Chemical elements
Category:Chemical elements with face-centered cubic structure
Category:Halogens
Category:Synthetic elements |
Astatine | Table of Content | Featured article, Characteristics, Physical, Chemical, Compounds, History, Isotopes, Natural occurrence, Synthesis, Formation, Separation methods, Dry, Wet, Uses and precautions, See also, Notes, References, Bibliography, External links |
Atom | Short description | Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that co... |
Atom | History of atomic theory | History of atomic theory |
Atom | In philosophy | In philosophy
The basic idea that matter is made up of tiny indivisible particles is an old idea that appeared in many ancient cultures. The word atom is derived from the ancient Greek word atomos, which means "uncuttable". But this ancient idea was based in philosophical reasoning rather than scientific reasoning. ... |
Atom | Dalton's law of multiple proportions | Dalton's law of multiple proportions
thumb|right|Various atoms and molecules from A New System of Chemical Philosophy (John Dalton 1808).
In the early 1800s, John Dalton compiled experimental data gathered by him and other scientists and discovered a pattern now known as the "law of multiple proportions". He noticed ... |
Atom | Discovery of the electron | Discovery of the electron
In 1897, J. J. Thomson discovered that cathode rays can be deflected by electric and magnetic fields, which meant that cathode rays are not a form of light but made of electrically charged particles, and their charge was negative given the direction the particles were deflected in. He measur... |
Atom | Discovery of the nucleus | Discovery of the nucleus
thumb|right|The Rutherford scattering experiments: The extreme scattering of some alpha particles suggested the existence of a nucleus of concentrated charge.
The electrons in the atom logically had to be balanced out by a commensurate amount of positive charge, but Thomson had no idea where... |
Atom | Bohr model | Bohr model
right|thumb|The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete.
A problem in classical mechanics is that an accelerating charged particle radiates electromagnetic radiation, ... |
Atom | Discovery of protons and neutrons | Discovery of protons and neutrons
Back in 1815, William Prout observed that the atomic weights of many elements were multiples of hydrogen's atomic weight, which is in fact true for all of them if one takes isotopes into account. In 1898, J. J. Thomson found that the positive charge of a hydrogen ion is equal to the ... |
Atom | The current consensus model | The current consensus model
thumb|right|The modern model of atomic orbitals draws zones where an electron is most likely to be found at any moment.
In 1925, Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics (matrix mechanics). One year earlier, Louis de Broglie had propose... |
Atom | Structure | Structure |
Atom | Subatomic particles | Subatomic particles
Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton, and the neutron.
The electron is the least massive of t... |
Atom | Nucleus | Nucleus
thumb|The binding energy needed for a nucleon to escape the nucleus, for various isotopes
All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to femtometres, where is the total number of nucleons.... |
Atom | Electron cloud | Electron cloud
right|thumb|A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.
The electrons in an atom are attracted to the protons in the nucleus by the e... |
Atom | Properties | Properties |
Atom | Nuclear properties | Nuclear properties
By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but iso... |
Atom | Mass | Mass
The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example ... |
Atom | Shape and size | Shape and size
Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. This assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or ... |
Atom | Radioactive decay | Radioactive decay
right|thumb|This diagram shows the half-life (T) of various isotopes with Z protons and N neutrons.
Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur wh... |
Atom | Magnetic moment | Magnetic moment
Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is m... |
Atom | Energy levels | Energy levels
thumb|right|These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. The top of the diagram is lower than an unbound electron state.
The potential energy of an electron in an atom is negative relative to when the distance from the nucl... |
Atom | Valence and bonding behavior | Valence and bonding behavior
Valency is the combining power of an element. It is determined by the number of bonds it can form to other atoms or groups. The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in
that shell are called valence electrons. The num... |
Atom | States | States
right|thumb|Graphic illustrating the formation of a Bose–Einstein condensate
Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases, and plasmas. W... |
Atom | Identification | Identification
right|thumb|Scanning tunneling microscope surface reconstruction image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them.
While atoms are too small to be seen, device... |
Atom | Origin and current state | Origin and current state
Baryonic matter forms about 4% of the total energy density of the observable universe, with an average density of about 0.25 particles/m3 (mostly protons and electrons). Within a galaxy such as the Milky Way, particles have a much higher concentration, with the density of matter in the inters... |
Atom | Formation | Formation
thumb|600px|Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae ... |
Atom | Earth | Earth
Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiom... |
Atom | Rare and theoretical forms | Rare and theoretical forms |
Atom | Superheavy elements | Superheavy elements
All nuclides with atomic numbers higher than 82 (lead) are known to be radioactive. No nuclide with an atomic number exceeding 92 (uranium) exists on Earth as a primordial nuclide, and heavier elements generally have shorter half-lives. Nevertheless, an "island of stability" encompassing relative... |
Atom | Exotic matter | Exotic matter
Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each ... |
Atom | See also | See also |
Atom | Notes | Notes |
Atom | References | References |
Atom | Bibliography | Bibliography
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Atom | Further reading | Further reading
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Atom | External links | External links
Atoms in Motion – The Feynman Lectures on Physics
Category:Chemistry
Category:Articles containing video clips |