Lanthanum

Atomic properties
Atomic number	57
Standard atomic weight	138.905 47(7)
Electron configuration	[Xe] 5d1 6s2
Physical properties
Melting point	920 °C (1193 K)
Boiling point	3420 °C (3693 K)
Density	6.17 g cm−3 (20 °C)
Electric resistivity	57–80 μΩ cm
Chemical properties
Electronegativity	1.10 (Pauling)
Solubility in water	reacts
Ionization energy
	5.5770(6) eV; 538.10(6) kJ mol−1
Electron affinity
	0.470(20) eV; 45.3(19) kJ mol−1
Atomic radii
Covalent radius	207 pm
Metallic radius	187 pm
Ionic radius	117.2 pm (La3+, Oh)
Thermodynamic properties
Standard entropy	56.8 J K−1 mol−1
Enthalpy change of atomization	423(6) kJ mol−1
Enthalpy change of fusion	8.5 kJ mol−1
Enthalpy change of vaporization	402 kJ mol−1
Miscellaneous
CAS number	7439-91-0
EC number	231-099-0
	Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).
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barium ← lanthanum → cerium

Y
↑
La
↓
Ac

Lanthanum (symbol: La) is a chemical element, one of the transition metals and also a lanthanoid and a rare earth element.

Notes and references

↑ ^1.0 ^1.1 ^1.2 ^1.3 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1102–10. ISBN 0-08-022057-6.
↑ Allred, A. L. Electronegativity values from thermochemical data. J. Inorg. Nucl. Chem. 1961, 17 (3–4), 215–21. DOI: 10.1016/0022-1902(61)80142-5.
↑ Martin, W. C.; Zalubas, R.; Hagan, L. Atomic energy levels – the rare earth elements. Natl. Stand. Ref. Data Ser. (U.S., Natl. Bur. Stand.) 1978, 60, 1–411.
↑ Covington, A. M.; Calabrese, D.; Thompson, J. S.; Kvale, T. J. Measurement of the electron affinity of lanthanum. J. Phys. B: At., Mol. Opt. Phys. 1998, 31 (20), L855–60. DOI: 10.1088/0953-4075/31/20/002.
↑ Cordero, Beatriz; Gómez, Verónica; Platero-Prats, Ana E.; Revés, Marc; Echeverría, Jorge; Cremades, Eduard; Barragán, Flavia; Alvarez, Santiago Covalent radii revisited. Dalton Trans. 2008 (5), 2832–38. DOI: 10.1039/b801115j.
↑ Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halids and chalcogenides. Acta Crystallogr. A 1976, 32 (5), 751–67. DOI: 10.1107/S0567739476001551.
↑ Jolly, William L. Modern Inorganic Chemistry, 2nd ed.; McGraw-Hill: New York, 1991; p 586. ISBN 0-07-032768-8.

See also the corresponding article on Wikipedia.

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