Yttrium is a chemical element; it has symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a rare-earth element. Yttrium is almost always found in combination with lanthanide elements in rare-earth minerals and is never found in nature as a free element. Y is the only stable isotope and the only isotope found in the Earth's crust.
The most important present-day use of yttrium is as a component of phosphors, especially those used in LEDs. Historically, it was once widely used in the red phosphors in television set cathode ray tube displays. Yttrium is also used in the production of electrodes, electrolytes, electronic filters, lasers, superconductors, various medical applications, and tracing various materials to enhance their properties.
Yttrium has no known biological role. Exposure to yttrium compounds can cause lung disease in humans.
Etymology The element is named after ytterbite, a mineral first identified in 1787 by chemist Carl Axel Arrhenius. He named the mineral after the village of Ytterby, in Sweden, where it had been discovered. When one of the chemicals in ytterbite was later found to be a previously unidentified element, the element was then named yttrium after the mineral.
Characteristics Properties Yttrium is a soft, silver-metallic, lustrous and highly crystalline transition metal in group 3. As expected by periodic trends, it is less electronegative than its predecessor in the group, scandium, and less electronegative than the next member of period 5, zirconium. However, due to the lanthanide contraction, it is also less electronegative than its successor in the group, lutetium.The electronegativity of both scandium and yttrium are between europium and gadolinium. Yttrium is the first d-block element in the fifth period.
The pure element is relatively stable in air in bulk form, due to passivation of a protective oxide () film that forms on the surface. This film can reach a thickness of 10 μm when yttrium is heated to 750 °C in water vapor. When finely divided, however, yttrium is very unstable in air; shavings or turnings of the metal can ignite in air at temperatures exceeding 400 °C. Yttrium nitride (YN) is formed when the metal is heated to 1000 °C in nitrogen.
Similarity to the lanthanides
The similarities of yttrium to the lanthanides are so strong that the element has been grouped with them as a rare-earth element, and is always found in nature together with them in rare-earth minerals.Emsley 2001, p. 498 Chemically, yttrium resembles those elements more closely than its neighbor in the periodic table, scandium,Daane 1968, p. 810. and if physical properties were plotted against atomic number, it would have an apparent number of 64.5 to 67.5, placing it between the lanthanides gadolinium and erbium.Daane 1968, p. 815.
It often also falls in the same range for reaction order, resembling terbium and dysprosium in its chemical reactivity. Yttrium is so close in size to the so-called 'yttrium group' of heavy lanthanide ions that in solution, it behaves as if it were one of them. Even though the lanthanides are one row farther down the periodic table than yttrium, the similarity in atomic radius may be attributed to the lanthanide contraction.
One of the few notable differences between the chemistry of yttrium and that of the lanthanides is that yttrium is almost exclusively trivalent, whereas about half the lanthanides can have valences other than three; nevertheless, only for four of the fifteen lanthanides are these other valences important in aqueous solution (Ce, Sm, Eu, and Yb).Daane 1968, p. 817
Compounds and reactions
As a trivalent transition metal, yttrium forms various inorganic compounds, generally in the +3 oxidation state, by giving up all three of its valence electrons. A good example is yttrium(III) oxide (), also known as yttria, a six-coordinate white solid.
Yttrium forms a water-insoluble fluoride, hydroxide, and oxalate, but its bromide, chloride, iodide, nitrate and sulfate are all soluble in water. The Y ion is colorless in solution due to the absence of electrons in the d and f electron shells.
Water readily reacts with yttrium and its compounds to form . Concentrated nitric and hydrofluoric acids do not rapidly attack yttrium, but other strong acids do.
With halogens, yttrium forms trihalides such as yttrium(III) fluoride (), yttrium(III) chloride (), and yttrium(III) bromide () at temperatures above roughly 200 °C. Similarly, carbon, phosphorus, selenium, silicon and sulfur all form binary compounds with yttrium at elevated temperatures.
Organoyttrium chemistry is the study of compounds containing carbon–yttrium bonds. A few of these are known to have yttrium in the oxidation state 0. (The +2 state has been observed in chloride melts, and +1 in oxide clusters in the gas phase.) Some trimerization reactions were generated with organoyttrium compounds as catalysts. These syntheses use as a starting material, obtained from and concentrated hydrochloric acid and ammonium chloride.
Hapticity is a term to describe the coordination of a group of contiguous atoms of a ligand bound to the central atom; it is indicated by the Greek letter eta, η. Yttrium complexes were the first examples of complexes where carboranyl ligands were bound to a d-metal center through a η-hapticity. Vaporization of the graphite intercalation compounds graphite–Y or graphite– leads to the formation of endohedral fullerenes such as Y@C. Electron spin resonance studies indicated the formation of Y and (C) ion pairs. The carbides YC, YC, and YC can be hydrolyzed to form hydrocarbons.
Isotopes and nucleosynthesis
Yttrium in the Solar System was created by stellar nucleosynthesis, mostly by the s-process (≈72%), but also the r-process (≈28%). The r-process consists of rapid neutron capture by lighter elements during supernova explosions. The s-process is a slow neutron capture of lighter elements inside pulsating red giant stars.
Yttrium isotopes are among the most common products of the nuclear fission of uranium in nuclear explosions and nuclear reactors. In the context of nuclear waste management, the most important isotopes of yttrium are Y and Y, with half-lives of 58.51 days and 64 hours, respectively. Though Y has a short half-life, it exists in secular equilibrium with its long-lived parent isotope, strontium-90 (Sr) (half-life 29 years).
All group 3 elements have an odd atomic number, and therefore few stable isotopes. Scandium has one stable isotope, and yttrium itself has only one stable isotope, Y, which is also the only isotope that occurs naturally. However, the lanthanide rare earths contain elements of even atomic number and many stable isotopes. Yttrium-89 is thought to be more abundant than it otherwise would be, due in part to the s-process, which allows enough time for isotopes created by other processes to decay by electron emission (neutron → proton).
Such a slow process tends to favor isotopes with atomic mass numbers (A = protons + neutrons) around 90, 138 and 208, which have unusually stable atomic nuclei with 50, 82, and 126 neutrons, respectively. This stability is thought to result from their very low neutron-capture cross-section. Electron emission of isotopes with those mass numbers is simply less prevalent due to this stability, resulting in them having a higher abundance. Y has a mass number close to 90 and has 50 neutrons in its nucleus.
At least 32 synthetic isotopes of yttrium have been observed, and these range in atomic mass number from 76 to 108. The least stable of these is Y with a half-life of 25 ms and the most stable is Y with half-life 106.629 days. Apart from Y, Y, and Y, with half-lives of 58.51 days, 79.8 hours, and 64 hours, respectively; all other isotopes have half-lives of less than a day and most of less than an hour.
Yttrium isotopes with mass numbers at or below 88 decay mainly by positron emission (proton → neutron) to form strontium (Z = 38) isotopes. Yttrium isotopes with mass numbers at or above 90 decay mainly by electron emission (neutron → proton) to form zirconium (Z = 40) isotopes. Isotopes with mass numbers at or above 97 are also known to have minor decay paths of β delayed neutron emission.
Yttrium has at least 20 metastable ("excited") isomers ranging in mass number from 78 to 102. Multiple excitation states have been observed for Y and Y. While most yttrium isomers are expected to be less stable than their ground state; Y have longer half-lives than their ground states, as these isomers decay by beta decay rather than isomeric transition.
History In 1787, part-time chemist Carl Axel Arrhenius found a heavy black rock in an old quarry near the Swedish village of Ytterby (now part of the Stockholm Archipelago). Thinking it was an unknown mineral containing the newly discovered element tungsten,Emsley 2001, p. 496 he named it ytterbite and sent samples to various chemists for analysis.Van der Krogt 2005
Johan Gadolin at the Royal Academy of Åbo (Turku) identified a new oxide (or "earth") in Arrhenius' sample in 1789, and published his completed analysis in 1794.Gadolin 1794 Anders Gustaf Ekeberg confirmed the identification in 1797 and named the new oxide yttria. In the decades after Antoine Lavoisier developed the first modern definition of chemical elements, it was believed that earths could be reduced to their elements, meaning that the discovery of a new earth was equivalent to the discovery of the element within, which in this case would have been yttrium.
Friedrich Wöhler is credited with first isolating the metal in 1828 by reacting a volatile chloride that he believed to be yttrium chloride with potassium.Heiserman, David L. (1992). "Element 39: Yttrium". Exploring Chemical Elements and their Compounds. New York: TAB Books. pp. 150–152. .
In 1843, Carl Gustaf Mosander found that samples of yttria contained three oxides: white yttrium oxide (yttria), yellow terbium oxide (confusingly, this was called 'erbia' at the time) and rose-colored erbium oxide (called 'terbia' at the time). A fourth oxide, ytterbium oxide, was isolated in 1878 by Jean Charles Galissard de Marignac. New elements were later isolated from each of those oxides, and each element was named, in some fashion, after Ytterby, the village near the quarry where they were found (see ytterbium, terbium, and erbium). In the following decades, seven other new metals were discovered in "Gadolin's yttria". Since yttria was found to be a mineral and not an oxide, Martin Heinrich Klaproth renamed it gadolinite in honor of Gadolin.
Until the early 1920s, the chemical symbol Yt was used for the element, after which Y came into common use.
In 1987, yttrium barium copper oxide was found to achieve high-temperature superconductivity. It was only the second material known to exhibit this property, and it was the first-known material to achieve superconductivity above the (economically important) boiling point of nitrogen.
Occurrence
Abundance Yttrium is found in most rare-earth minerals, and some uranium ores, but never in the Earth's crust as a free element. About 31 ppm of the Earth's crust is yttrium, making it the 43rd most abundant element. Yttrium is found in soil in concentrations between 10 and 150 ppm (dry weight average of 23 ppm) and in sea water at 9 ppt. Lunar rock samples collected during the American Apollo Project have a relatively high content of yttrium.Stwertka 1998, p. 115.
Yttrium is not considered a "bone-seeker" like strontium and lead. Normally, as little as is found in the entire human body; human breast milk contains 4 ppm. Yttrium can be found in edible plants in concentrations between 20 ppm and 100 ppm (fresh weight), with cabbage having the largest amount. With as much as 700 ppm, the seeds of woody plants have the highest known concentrations.