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   yttrium is the chemical element with atomic number 39, of symbol Y. Yttrium is a transition element of metallic appearance, which has a chemical behavior close to that of lanthanides, and historically classified among the rare earths, with scandium and lanthanides7. In nature, it never occurs in its native state, but most often combined with lanthanides in rare earth ores. Its only stable isotope is 89Y. It is also the only natural isotope.

Yttrium was discovered in 1789 as an oxide by Johan Gadolin8 in a gadolinite sample discovered by Carl Axel Arrhenius. Anders Gustaf Ekeberg named this new yttria oxide. It was first isolated in 1828 by Friedrich Wöhler9.

The most important use of yttrium is the manufacture of phosphors, such as those used in cathode ray tube televisions or LEDs10. Its other applications include the production of electrodes, electrolytes, electronic filters, lasers and superconductive materials, and various medical applications. Yttrium plays no known biological role, but exposure can cause lung disease in humans11.
Yttrium has 33 known isotopes, with a mass number varying between 76 and 108, and 29 nuclear isomers. Among these isotopes, only one is stable, 89Y, and constitutes all of the naturally present yttrium, making yttrium a monoisotopic element and also a mononucleidic element. Its standard atomic mass is therefore the isotopic mass of 89Y, i.e. 88.905 85 (2) u.
Yttrium is a soft metal, metallic in appearance, belonging to elements of group 3 of the periodic table. As expected from the periodicity of the properties, it is less electronegative than scandium and zirconium, but more electronegative than lanthanum21,22. It is the first element of group d of the fifth period of the classification.

Pure yttrium is relatively stable in air in massive form due to the formation of a passivation layer of yttrium oxide on its surface. This film can reach a thickness of 10 micrometers when heated to 750 กใ C in the presence of water vapor23. Reduced to powder or chips, the yttrium is not stable in air, and can ignite spontaneously if the temperature exceeds 400 กใ C9. When heated to 1000 กใ C under nitrogen, yttrium nitride YN23 is formed.

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rhenium    germanium    zirconium     cadmium     hafnium

      barium   lithium     beryllium     strontium     calcium

      Tantalum    gadolinium    samarium      yttrium   ytterbium

       Lutetium    praseodymium   holmium     erbium   thulium     dysprosium

       terbium   europium  lanthanum   cerium   neodymium  scandium 

         rubidium    cesium

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