Europium

Europium, ₆₃Eu
Europium
Pronunciation	/jʊˈroʊpiəm/ ⓘ (yuu-ROH-pee-əm)
Appearance	silvery white, with a pale yellow tint; but rarely seen without oxide discoloration
Standard atomic weight Ar°(Eu)
	151.964±0.001; 151.96±0.01 (abridged);
Europium in the periodic table
Atomic number (Z)	63
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f7 6s2
Electrons per shell	2, 8, 18, 25, 8, 2
Physical properties
Phase at STP	solid
Melting point	1099 K (826 °C, 1519 °F)
Boiling point	1802 K (1529 °C, 2784 °F)
Density (at 20° C)	5.246 g/cm3
when liquid (at m.p.)	5.13 g/cm3
Heat of fusion	9.21 kJ/mol
Heat of vaporization	176 kJ/mol
Molar heat capacity	27.66 J/(mol·K)
Atomic properties
Oxidation states	common: +2, +3; 0
Electronegativity	Pauling scale: 1.2
Ionization energies	1st: 547.1 kJ/mol ; 2nd: 1085 kJ/mol ; 3rd: 2404 kJ/mol ; ;
Atomic radius	empirical: 180 pm
Covalent radius	198±6 pm
	Spectral lines of europium
Other properties
Natural occurrence	primordial
Crystal structure	body-centered cubic (bcc) (cI2)
Lattice constant	a = 458.22 pm (at 20 °C)
Thermal expansion	26.3×10−6/K (at 20 °C)
Thermal conductivity	est. 13.9 W/(m⋅K)
Electrical resistivity	poly: 0.900 µΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+34000.0×10−6 cm3/mol
Young's modulus	18.2 GPa
Shear modulus	7.9 GPa
Bulk modulus	8.3 GPa
Poisson ratio	0.152
Vickers hardness	165–200 MPa
CAS Number	7440-53-1
History
Naming	after Europe
Discovery	Eugène-Anatole Demarçay (1896)
First isolation	1937
Isotopes of europium
β−	152Gd
ε	154Sm

Europium is a chemical element; it has symbol Eu and atomic number 63. It is a silvery-white metal of the lanthanide series that reacts readily with air to form a dark oxide coating. Europium is the most chemically reactive, least dense, and softest of the lanthanides. It is soft enough to be cut with a knife. Europium was discovered in 1896, provisionally designated as Σ; in 1901, it was named after the continent of Europe.^[9] Europium usually assumes the oxidation state +3, like other members of the lanthanide series, but compounds having oxidation state +2 are also common. All europium compounds with oxidation state +2 are slightly reducing. Europium has no significant biological role but is relatively non-toxic compared to other heavy metals. Most applications of europium exploit the phosphorescence of europium compounds. Europium is one of the rarest of the rare-earth elements on Earth.^[10]

^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
^ "Standard Atomic Weights: Europium". CIAAW. 1995.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ ^a ^b ^c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.
^ "Periodic Table: Europium". Royal Society of Chemistry.
^ Stwertka, Albert. A Guide to the Elements, Oxford University Press, 1996, p. 156. ISBN 0-19-508083-1

[1] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.

[CIAAWeuropium-2] "Standard Atomic Weights: Europium". CIAAW. 1995.

[CIAAW2021-3] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[Arblaster_2018-4] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[Cloke1993-5] Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.

[magnet-6] Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[7] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[NUBASE2020-8] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3) 030001. doi:10.1088/1674-1137/abddae.

[eu-9] "Periodic Table: Europium". Royal Society of Chemistry.

[Stwertka-10] Stwertka, Albert. A Guide to the Elements, Oxford University Press, 1996, p. 156. ISBN 0-19-508083-1

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