Lanthanum

Lanthanum, 57La
Lanthanum
Pronunciation/ˈlænθənəm/ (LAN-thə-nəm)
Appearancesilvery white
Standard atomic weight Ar°(La)
Lanthanum in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


La

Ac
bariumlanthanumcerium
Atomic number (Z)57
Groupf-block groups (no number)
Periodperiod 6
Block  f-block
Electron configuration[Xe] 5d1 6s2
Electrons per shell2, 8, 18, 18, 9, 2
Physical properties
Phase at STPsolid
Melting point1193 K ​(920 °C, ​1688 °F)
Boiling point3737 K ​(3464 °C, ​6267 °F)
Density (at 20° C)6.145 g/cm3[3]
when liquid (at m.p.)5.94 g/cm3
Heat of fusion6.20 kJ/mol
Heat of vaporization400 kJ/mol
Molar heat capacity27.11 J/(mol·K)
Vapor pressure (extrapolated)
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2005 2208 2458 2772 3178 3726
Atomic properties
Oxidation states0,[4] +1,[5] +2, +3 (a strongly basic oxide)
ElectronegativityPauling scale: 1.10
Ionization energies
  • 1st: 538.1 kJ/mol
  • 2nd: 1067 kJ/mol
  • 3rd: 1850.3 kJ/mol
Atomic radiusempirical: 187 pm
Covalent radius207±8 pm
Color lines in a spectral range
Spectral lines of lanthanum
Other properties
Natural occurrenceprimordial
Crystal structureα form: ​double hexagonal close-packed (dhcp) (hP4)
Lattice constants
Double hexagonal close packed crystal structure for α form: lanthanum
a = 0.37742 nm
c = 1.2171 nm (at 20 °C)[3]
Thermal expansion5.1×10−6/K (at 20 °C)[3][a]
Thermal conductivity13.4 W/(m⋅K)
Electrical resistivityα, poly: 615 nΩ⋅m (at r.t.)
Magnetic orderingparamagnetic[6]
Molar magnetic susceptibility+118.0×10−6 cm3/mol (298 K)[7]
Young's modulusα form: 36.6 GPa
Shear modulusα form: 14.3 GPa
Bulk modulusα form: 27.9 GPa
Speed of sound thin rod2475 m/s (at 20 °C)
Poisson ratioα form: 0.280
Mohs hardness2.5
Vickers hardness360–1750 MPa
Brinell hardness350–400 MPa
CAS Number7439-91-0
History
DiscoveryCarl Gustaf Mosander (1838)
Isotopes of lanthanum
Main isotopes[8] Decay
abun­dance half-life (t1/2) mode pro­duct
137La synth 6×104 y ε 137Ba
138La 0.089%
Preview warning: Infobox La isotopes: Abundance percentage not recognised "na=0.089%" cat#%
1.05×1011 y ε 138Ba
β 138Ce
139La 99.911%
Preview warning: Infobox La isotopes: Abundance percentage not recognised "na=99.911%" cat#%
stable
 Category: Lanthanum
| references

Lanthanum is a chemical element; it has symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. Like most other rare earth elements, the usual oxidation state is +3, although some compounds are known with an oxidation state of +2. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.

Lanthanum usually occurs together with cerium and the other rare earth elements. Lanthanum was first found by the Swedish chemist Carl Gustaf Mosander in 1839 as an impurity in cerium nitrate – hence the name lanthanum, from the Ancient Greek λανθάνειν (lanthanein), meaning 'to lie hidden'. Although it is classified as a rare earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as lead. In minerals such as monazite and bastnäsite, lanthanum composes about a quarter of the lanthanide content.[9] It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923.

Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon arc lamps for studio lights and projectors, ignition elements in lighters and torches, electron cathodes, scintillators, gas tungsten arc welding electrodes, and other things. Lanthanum carbonate is used as a phosphate binder in cases of high levels of phosphate in the blood seen with kidney failure.

  1. ^ "Standard Atomic Weights: Lanthanum". CIAAW. 2005.
  2. ^ 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.
  3. ^ a b c d Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  4. ^ 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.
  5. ^ La(I), Pr(I), Tb(I), Tm(I), and Yb(I) have been observed in MB8 clusters; see Li, Wan-Lu; Chen, Teng-Teng; Chen, Wei-Jia; Li, Jun; Wang, Lai-Sheng (2021). "Monovalent lanthanide(I) in borozene complexes". Nature Communications. 12 (1): 6467. doi:10.1038/s41467-021-26785-9. PMC 8578558. PMID 34753931.
  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.
  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.
  9. ^ "Monazite-(Ce) Mineral Data". Webmineral. Retrieved 10 July 2016.


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).