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    Zirconium

    IsotopeAtomic mass (Da)Isotopic abundance (amount fraction)
    90Zr 89.904 70(2)0.5145(4)
    91Zr 90.905 64(2)0.1122(5)
    92Zr 91.905 03(2)0.1715(3)
    94Zr 93.906 31(2)0.1738(4)
    96Zr 95.908 27(2)0.0280(2)

    The atomic weight of Zr has been taken to be Ar(Zr) = 91.22 since 1931, and this value was reconfirmed in 1969 when it was assessed as 91.22(1). Since then, two isotopic composition measurements have been carried out Ar(Zr) = 91.224 with an estimated uncertainty of +0.002 and –0.005, and Ar(Zr) = 91.2235(5).

    SOURCE  Atomic weights of the elements: Review 2000 by John R de Laeter et al. Pure Appl. Chem. 2003 (75) 683-800
    © IUPAC 2003

    CIAAW

    Zirconium
    Ar(Zr) = 91.224(2) since 1983

    The name derives from the Arabic zargun for "gold-like". It was discovered in zirconia by the German chemist Martin-Heinrich Klaproth in 1789. Zirconium was first isolated by Swedish chemist Jöns Jacob Berzelius in 1824 in an impure state, and finally by the chemists D. Lely, Jr. and L. Hamburger in a pure state in 1914.