Lithium Wikipedia. Lithium from Greek lithos, stone is a chemical element with symbol Li and atomic number 3. Technetium is a chemical element with symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive none are stable. It is a soft, silvery white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut open, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in usually ionic compounds, such as pegmatitic minerals which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is commonly obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride. The nucleus of the lithium atom verges on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, lithium is less common in the solar system than 2. For related reasons, lithium has important uses in nuclear physics. The transmutation of lithium atoms to helium in 1. Astm Manual On Zirconium And Hafnium Bomb' title='Astm Manual On Zirconium And Hafnium Bomb' />Search metadata Search full text of books Search TV captions Search archived web sites Advanced Search. Lithium and its compounds have several industrial applications, including heat resistant glass and ceramics, lithium grease lubricants, flux additives for iron, steel and aluminium production, lithium batteries, and lithium ion batteries. These uses consume more than three quarters of lithium production. Lithium is present in biological systems in trace amounts its functions are uncertain. Lithium salts have proven to be useful as a mood stabilizing drug in the treatment of bipolar disorder in humans. PropertieseditAtomic and physicaledit. Lithium ingots with a thin layer of black nitride tarnish. Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cation. Because of this, lithium is a good conductor of heat and electricity as well as a highly reactive element, though it is the least reactive of the alkali metals. Lithiums low reactivity is due to the proximity of its valence electron to its nucleus the remaining two electrons are in the 1s orbital, much lower in energy, and do not participate in chemical bonds. Lithium metal is soft enough to be cut with a knife. When cut, it possesses a silvery white color that quickly changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals 1. C, it has the highest melting and boiling points of the alkali metals. Lithium has a very low density 0. It is the least dense of all elements that are solids at room temperature the next lightest solid element potassium, at 0. Furthermore, apart from helium and hydrogen, it is less dense than any liquid element, being only two thirds as dense as liquid nitrogen 0. Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being sodium and potassium. Lithiums coefficient of thermal expansion is twice that of aluminium and almost four times that of iron. Lithium is superconductive below 4. K at standard pressure9 and at higher temperatures more than 9 K at very high pressures 2. GPa. 1. 0 At temperatures below 7. K, lithium, like sodium, undergoes diffusionless phase change transformations. At 4. 2 K it has a rhombohedral crystal system with a nine layer repeat spacing at higher temperatures it transforms to face centered cubic and then body centered cubic. At liquid helium temperatures 4 K the rhombohedral structure is prevalent. Multiple allotropic forms have been identified for lithium at high pressures. Lithium has a mass specific heat capacity of 3. Because of this, lithium metal is often used in coolants for heat transfer applications. Chemistry and compoundseditLithium reacts with water easily, but with noticeably less vigor than other alkali metals. The reaction forms hydrogen gas and lithium hydroxide in aqueous solution. Because of its reactivity with water, lithium is usually stored in a hydrocarbon sealant, often petroleum jelly. Though the heavier alkali metals can be stored in more dense substances, such as mineral oil, lithium is not dense enough to be fully submerged in these liquids. In moist air, lithium rapidly tarnishes to form a black coating of lithium hydroxide Li. OH and Li. OHH2. O, lithium nitride Li. N and lithium carbonate Li. CO3, the result of a secondary reaction between Li. OH and CO2. 1. 6When placed over a flame, lithium compounds give off a striking crimson color, but when it burns strongly the flame becomes a brilliant silver. Lithium will ignite and burn in oxygen when exposed to water or water vapors. Lithium is flammable, and it is potentially explosive when exposed to air and especially to water, though less so than the other alkali metals. The lithium water reaction at normal temperatures is brisk but nonviolent because the hydrogen produced does not ignite on its own. As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers Class D type. Lithium is one of the few metals that react with nitrogen under normal conditions. Lithium has a diagonal relationship with magnesium, an element of similar atomic and ionic radius. Chemical resemblances between the two metals include the formation of a nitride by reaction with N2, the formation of an oxide Li. O and peroxide Li. O2 when burnt in O2, salts with similar solubilities, and thermal instability of the carbonates and nitrides. The metal reacts with hydrogen gas at high temperatures to produce lithium hydride Li. H. 2. 1Other known binary compounds include halides Li. F, Li. Cl, Li. Br, Li. I, sulfide Li. 2S, superoxide Li. O2, and carbide Li. C2. Many other inorganic compounds are known in which lithium combines with anions to form salts borates, amides, carbonate, nitrate, or borohydride Li. BH4. Lithium aluminium hydride Li. Al. H4 is commonly used as a reducing agent in organic synthesis. Multiple organolithium reagents are known in which there is a direct bond between carbon and lithium atoms, effectively creating a carbanion. These are extremely powerful bases and nucleophiles. In many of these organolithium compounds, the lithium ions tend to aggregate into high symmetry clusters by themselves, which is relatively common for alkali cations. Li. He, a very weakly interacting van der Waals compound, has been detected at very low temperatures. IsotopeseditNaturally occurring lithium is composed of two stable isotopes, 6. Li and 7. Li, the latter being the more abundant 9. Both natural isotopes have anomalously low nuclear binding energy per nucleon compared to the neighboring elements on the periodic table, helium and beryllium lithium is the only low numbered element that can produce net energy through nuclear fission. The two lithium nuclei have lower binding energies per nucleon than any other stable nuclides other than deuterium and helium 3. As a result of this, though very light in atomic weight, lithium is less common in the Solar System than 2. Seven radioisotopes have been characterized, the most stable being 8. Li with a half life of 8. Li with a half life of 1. All of the remaining radioactive isotopes have half lives that are shorter than 8. The shortest lived isotope of lithium is 4. Li, which decays through proton emission and has a half life of 7. Li is one of the primordial elements or, more properly, primordial nuclides produced in Big Bang nucleosynthesis. A small amount of both 6. Li and 7. Li are produced in stars, but are thought to be burned as fast as produced. Additional small amounts of lithium of both 6. Li and 7. Li may be generated from solar wind, cosmic rays hitting heavier atoms, and from early solar system 7. Be and 1. 0Be radioactive decay. Technetium Wikipedia. Technetium,  4. 3Tc. General properties. Pronunciationtek NEE shee m. Appearanceshiny gray metal. Mass number. 98 most stable isotopeTechnetium in the periodic table. Atomic numberZ4. Group, periodgroup 7, period 5. Blockd block. Element category transition metal. Electron configurationKr 4d. Electrons per shell. Physical properties. Phaseat STPsolid. Melting point. 24. K 2. 15. 7 C, 3. FBoiling point. K 4. 26. 5 C, 7. FDensitynear r. Heat of fusion. 33. Jmol. Heat of vaporization. Jmol. Molar heat capacity. JmolKVapor pressureextrapolatedP Pa1. T K2. 72. 72. 99. Atomic properties. Oxidation states. Electronegativity. Pauling scale 1. Ionization energies. Jmol. 2nd 1. 47. Jmol. Jmol. Atomic radiusempirical 1. Covalent radius. 14. Miscellanea. Crystal structurehexagonal close packed hcp. Speed of soundthin rod. Msha Toolbox Topics Free Download. CThermal expansion. K2 at r. t. Thermal conductivity. WmKElectrical resistivity. CMagnetic ordering. Paramagnetic. Magnetic susceptibility2. K3CAS Number. 74. History. Prediction. Dmitri Mendeleev1. Discovery and first isolation. Emilio Segr and Carlo Perrier 1. Main isotopes of technetium. Wikidata. Technetium is a chemical element with symbol Tc and atomic number 4. It is the lightest element whose isotopes are all radioactive none are stable. Nearly all technetium is produced synthetically, and only minute amounts are found in the Earths crust. Naturally occurring technetium is a spontaneous fission product in uranium ore or the product of neutron capture in molybdenum ores. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese. Many of technetiums properties were predicted by Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese Em. In 1. 93. 7, technetium specifically the technetium 9. Greek, meaning artificial, ium. One short lived gamma ray emitting nuclear isomer of technetiumtechnetium 9. The ground state of this nuclide, technetium 9. Long lived technetium isotopes produced commercially are by products of the fission of uranium 2. Because no isotope of technetium has a half life longer than 4. HistoryeditSearch for element 4. From the 1. 86. 0s through 1. Dmitri Mendeleev contained a gap between molybdenum element 4. In 1. 87. 1, Mendeleev predicted this missing element would occupy the empty place below manganese and have similar chemical properties. Mendeleev gave it the provisional name ekamanganese from eka, the Sanskrit word for one because the predicted element was one place down from the known element manganese. Many early researchers, both before and after the periodic table was published, were eager to be the first to discover and name the missing element. Its location in the table suggested that it should be easier to find than other undiscovered elements. Irreproducible resultsedit. Periodisches System der Elemente 1. Gdask University of Technology lack of elements 8. Po though discovered as early as in 1. Maria Sklodowska Curie, 8. At 1. 94. 0, in Berkeley, 8. Fr 1. 93. 9, in France, 9. Np 1. 94. 0, in Berkeley and other actinides and lanthanides. Old symbols for 1. Ar here A, 4. 3 technetium Tc Ma, masurium, 1. Palermo, 5. 4 xenon Xe X, 8. Rn Em, emanationGerman chemists Walter Noddack, Otto Berg, and Ida Tacke reported the discovery of element 7. Masuria in eastern Prussia, now in Poland, the region where Walter Noddacks family originated. The group bombarded columbite with a beam of electrons and deduced element 4. X ray diffraction spectrograms. The wavelength of the X rays produced is related to the atomic number by a formula derived by Henry Moseley in 1. The team claimed to detect a faint X ray signal at a wavelength produced by element 4. Later experimenters could not replicate the discovery, and it was dismissed as an error for many years. Still, in 1. 93. 3, a series of articles on the discovery of elements quoted the name masurium for element 4. Whether the 1. 92. Official discovery and later historyeditThe discovery of element 4. December 1. 93. 6 experiment at the University of Palermo in Sicily by Carlo Perrier and Emilio Segr. In mid 1. 93. 6, Segr visited the United States, first Columbia University in New York and then the Lawrence Berkeley National Laboratory in California. He persuaded cyclotron inventor Ernest Lawrence to let him take back some discarded cyclotron parts that had become radioactive. Lawrence mailed him a molybdenum foil that had been part of the deflector in the cyclotron. Segr enlisted his colleague Perrier to attempt to prove, through comparative chemistry, that the molybdenum activity was indeed from an element with the atomic number 4. In 1. 93. 7 they succeeded in isolating the isotopestechnetium 9. University of Palermo officials wanted them to name their discovery panormium, after the Latin name for Palermo, Panormus. In 1. 94. 71. 5 element 4. Greek word, meaning artificial, since it was the first element to be artificially produced. Segr returned to Berkeley and met Glenn T. Seaborg. They isolated the metastable isotopetechnetium 9. In 1. 95. 2, astronomer Paul W. Merrill in California detected the spectral signature of technetium specifically wavelengths of 4. S typered giants. The stars were near the end of their lives, yet were rich in this short lived element, indicating that it was being produced in the stars by nuclear reactions. This evidence bolstered the hypothesis that heavier elements are the product of nucleosynthesis in stars. More recently, such observations provided evidence that elements are formed by neutron capture in the s process. Since that discovery, there have been many searches in terrestrial materials for natural sources of technetium. In 1. 96. 2, technetium 9. Belgian Congo in extremely small quantities about 0. The Oklonatural nuclear fission reactor contains evidence that significant amounts of technetium 9. CharacteristicseditPhysical propertieseditTechnetium is a silvery gray radioactive metal with an appearance similar to platinum, commonly obtained as a gray powder. The crystal structure of the pure metal is hexagonalclose packed. Atomic technetium has characteristic emission lines at these wavelengths of light 3. The metal form is slightly paramagnetic, meaning its magnetic dipoles align with external magnetic fields, but will assume random orientations once the field is removed. Pure, metallic, single crystal technetium becomes a type II superconductor at temperatures below 7. K. note 22. 3 Below this temperature, technetium has a very high magnetic penetration depth, greater than any other element except niobium. Chemical propertieseditTechnetium is located in the seventh group of the periodic table, between rhenium and manganese. As predicted by the periodic law, its chemical properties are between those two elements. Of the two, technetium more closely resembles rhenium, particularly in its chemical inertness and tendency to form covalent bonds. Unlike manganese, technetium does not readily form cations ions with a net positive charge. Technetium exhibits nine oxidation states from 1 to 7, with 4, 5, and 7 being the most common. Technetium dissolves in aqua regia, nitric acid, and concentrated sulfuric acid, but it is not soluble in hydrochloric acid of any concentration. Metallic technetium slowly tarnishes in moist air2. Technetium can catalyse the destruction of hydrazine by nitric acid, and this property is due to its multiplicity of valencies. This caused a problem in the separation of plutonium from uranium in nuclear fuel processing, where hydrazine is used as a protective reductant to keep plutonium in the trivalent rather than the more stable tetravalent state.