* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Scandium and Yttrium - Mercyhurst University
Nuclear chemistry wikipedia , lookup
Einsteinium wikipedia , lookup
Chemical element wikipedia , lookup
Electronegativity wikipedia , lookup
Gaseous signaling molecules wikipedia , lookup
Metallic bonding wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Isotopic labeling wikipedia , lookup
Flux (metallurgy) wikipedia , lookup
History of chemistry wikipedia , lookup
Organic chemistry wikipedia , lookup
Boron group wikipedia , lookup
Drug discovery wikipedia , lookup
Periodic table wikipedia , lookup
Organosulfur compounds wikipedia , lookup
Extended periodic table wikipedia , lookup
Chemistry: A Volatile History wikipedia , lookup
Alkaline earth metal wikipedia , lookup
Rare-earth element wikipedia , lookup
Surface properties of transition metal oxides wikipedia , lookup
Metalloprotein wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Coordination complex wikipedia , lookup
Inorganic chemistry wikipedia , lookup
IUPAC nomenclature of inorganic chemistry 2005 wikipedia , lookup
Scandium and Yttrium Junior Chemist CHEM 310 Final Paper November 18, 2008 Yttrium and Scandium Tables Element name Yttrium Density (g/cm3) 4.472 Symbol Y Melting Point (oC) 1526 Meaning of the Element’s name Johan Gadolin named it after the city in Sweden, Ytterby, where it was found.1 Boiling Point (oC) 3336 Crystal Structure hexagonal Discovery date 1794 (the oxide, Gadolin)2 1828 (pure form, Friedrich Wöhler)3 Electronegativity (Pauling scale) 1.22 Atomic Radius 162 Bottom half of table1 Element name Scandium Symbol Density (g/cm3) 2.985 Melting Point (oC) 1541 Sc Meaning of the Element’s name Lars F. Nilson named it after Scandanavia, where the mineral was first identified.1 Boiling Point (oC) 2836 Crystal Structure hexagonal Discovery date 1879 (the oxide, Nilson)1 1937 (pure form, Werner Fischer, Karl Brunger and Hans Grieneisen)3 Electronegativity (Pauling scale) 1.36 Atomic Radius 160 Bottom half of table1 Physical properties The pure metal of both Sc and Y are silvery in color and are somewhat air stable, less so as the temperature increases and less so as the surface area of the metal increases.4 Yttrium forms a protective oxide, and thus must be heated even moreso than scandium (to about 1000 oC) to initiate reaction.4 At room temperature, scandium metal turns a light yellow or pink color in air.1 It is not obvious what is causing the color as Sc3+ would be expected to be colorless (white) due to the lack of d-electrons. Purification and Properties The most interesting thing about these two elements is in their very convoluted discovery and isolation. It all started with a black rock found by the mineralogist Carl Axel Arrhenius in 1787 in a Ytterby quarry.2 The rock looked like coal but was quite dense and so was considered to contain tungsten (the densest element known at that time).1 Upon careful chemical analysis by many chemists (see Table) this mineral yielded the ‘earth’ of all of the lanthanides as well as scandium and yttrium.2 The simple black rock was, in fact, a very complex mixture! The lanthanides (as well as Sc and Y) all occur in nature as the +3 oxidation state and are all similar in size. Because of these two properties, the lanthanides, Sc and Y nearly always occur together in nature. Currently, the best source of the elements is by the reduction of the metal(III) fluoride with calcium: 2 MF3 + 3 Ca 2 M + 3 CaF2 where M = Sc or Y The pure metal of both Sc and Y are silvery in color and are somewhat air stable, less so as the temperature increases and less so as the surface area of the metal increases.4 Yttrium forms a protective oxide, and thus must be heated even moreso than scandium (to about 1000 oC) to initiate reaction.4 At room temperature, scandium metal turns a light yellow or pink color in air.1 It is not obvious what is causing the color as Sc3+ would be expected to be colorless (white) due to the lack of d-electrons. Chemistry Scandium and yttrium’s behavior in air has been discussed earlier. Both metals are fairly unreactive except when heated. Both metals react with dilute hydrochloric acid to form MCl3.5 2 M(s) + 6 HCl(aq) 2 MCl3(aq) + 3 H2(g) where M = Sc or Y The metals react with water slowly at room temperature, more rapidly upon heating, to form hydrogen gas,4 2 M(s) + 6 H2O(ℓ) 2 M(OH)3(s) + 3 H2(g) Scandium is more like aluminum than the other RE’s, being a Group IIIB transition metal (the neutral metal has three valence electrons). Scandium(III) oxide reacts with hydroxide base just as aluminum oxide does4, M’2O3 + OH– M’O(OH) + NaOH Na3[M’(OH)6]•2H2O where M’ = Al, Sc Both Sc and Y react readily with halogens to form MX3,5 M(s) + X2(g) MX3(s) where X = F, Cl, Br, or I Unlike AlCl3, ScCl3 does not act as a Friedel-Crafts catalyst,4 R–X + ScCl3 no reaction R R–X + AlCl3 R+ + AlCl3X– + H2O + HCl + Al salts where R = alkyl or acyl group and X is a halogen However scandium(III) triflate is a useful organic catalyst, made by reacting Sc2O3 with triflic acid,1 Sc2O3 + 6 CF3SO3H 2 Sc(CF3SO3)3 + 3 H2O As mentioned previously, the common oxidation state of Sc and Y is +3. Only scandium can form a lower oxidation state of +2, as MIScX3, but it is not very common.4 A coordination number of six for both Sc and Y is typical, but it can vary up to a value of nine.4 Scandium only has one known compound with a coordination number of nine, scandium(III) triflate nonahydrate.4 Both Sc and Y have one stable isotope found naturally. Scandium’s stable isotope is 45Sc (with 24 neutrons). Yttrium’s stable isotope is 89Y (with 50 neutrons). While there is no commercial use of any of yttrium’s isotopes, 46Sc is used in oil refinery crackers as a tracing agent.1 Other isotopes of these elements are man-made.1 Compounds and Their Uses Since their discovery, many uses of the compounds of scandium and yttrium have been found. Scandium(III) oxide is used for its heat and thermal shock resistance in high temperature systems such as ceramics.1 Yttrium(III) oxide or yttrium(III) vanadate, YVO4, doped with europium are the most widely used yttrium compounds. These doped compounds are used as the red phosphor in television picture tubes.1 Metal halides are often added to mercury vapor lamps to subtly change the color. Scandium(III) iodide (ScI3) makes the light from a mercury vapor lamp resemble sunlight. As mentioned, scandium(III) triflate (Sc(CF3SO3)3) is a useful Lewis acid in organic synthesis as it is water-stable.1 Current Research Much like transition metals ions, scandium(III) and yttrium(III) will coordinate to a variety of ligands, including crown ethers, aza-crown ethers and substituted tris(3,5-pyrazolyl) methane ligands.6, 7 These compounds are interesting because they can be used for competitive binding studies.7 J. Okuda et. al. have found that these charged compounds also show improved catalytic behavior towards ethylene, styrene and diene polymerization versus the neutral compounds.6 The X-ray diffraction studies show the RE’s typical coordination number (6) as well as higher coordination. Two compounds were particularly interesting, [Sc(CH2Si(CH3)3)3(12-crown-4)] (4) and Y(CH2Si(CH3)3)3(12-crown-4)] (5) (shown on the next page), because of their difference in coordination. [Sc(CH2Si(CH3)3)3(12-crown-4)], (4) [Y(CH2Si(CH3)3)3(12-crown-4)], (5) Compound (5) coordinates through all four oxygen atoms of the 12-crown-4, but compound (4) only coordinates through 3 oxygen atoms of the 12-crown-4 ligand.6 Bibliography 1 Web: Wikipedia, www.wikipedia.org (and references therein) (accessed July 2008). 2 Weeks, M. E. Discovery of the Elements; Published by the Journal of Chemical Education, Easton, 1968; Chapter 16. 3 Marshall, J. L. Discovery of the Elements: A Search for the Fundamental Principles of the Universe; Simon & Schuster Custom Publishing: Needham Heights, 1998; pp. 22 and 68. 4 Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry; John Wiley & Sons, Inc.: New York, 1999; pp. 1108-1125. 5 Web: WebelementsTM periodic table. http://www.webelements.com (accessed July 2008). 6 Elvidge, B. R.; Arndt, S.; Zeimentz, P. M.; Spaniol, T. P.; Okuda, J. Inorg. Chem. 2005, 44, 6777-6788. 7 Tredget, C. S.; Lawrence, S. C.; Ward, B. D.; Howe, R. G.; Cowley, A. R.; Mountford, P. Organomet. 2005, 24, 3136-3148.