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Lanthanum

What is Lanthanum

Lanthanum (pronunciation: LAN-the-nem) [3] is a soft, silvery rare-earth metal belonging to the lanthanoids family and represented by the chemical symbol La [1, 2]. Its main isotopes include the most abundant 139La (with 99.91% natural abundance) and the most stable 138La, the radioactive isotope with a half-life period of 1.06 X 1026 years [1, 4].

Lanthanum

Where can Lanthanum be Found

The element naturally occurs in bastnaesite and monazite, making up 38% and 25% of the rare-earth minerals respectively [1]. Isolation of lanthanum from these minerals involves solvent extraction and ion-exchange separation techniques [1]. The metal can be produced through calcium reduction of anhydrous fluoride [1]. The top 3 lanthanum producing countries include China, Russia, and Malaysia while the top 3 countries with the largest lanthanum reserves are China, CIS Countries, and the USA [1].

History

Origin of its Name: The name of the element is derived from the Greek word ‘lanthanein’, which means to lie hidden, as its existence in cerium oxide was long undetected [1].

Who discovered it: The Swedish chemist Carl Gustaf Mosander is credited with the discovery of lanthanum [1].

When and How was it Discovered

In January 1839, lanthanum was extracted by Carl Mosander while working on his sample of cerium at the Karolinska Institute in Sweden [1]. He took powdered cerium nitrate and treated it with dilute nitric acid [5]. He observed that some of the nitrate powder dissolved in the acid, and then he decided to isolate the mixture from the precipitate by using heat and sodium oxalate [5]. The pale brick-colored oxide obtained was given the name lanthana [3, 5].

Lanthanum Element Symbol

A student at the Karolinska Institute, Axel Erdmann discovered the element independently from a new mineral found in a Norwegian fjord [1, 5]. The new mineral was named mosandrite after Carl Mosander who produced impure lanthanum from anhydrous cerium chloride [5]. In 1923, pure lanthanum was obtained by Kremers and Stevens through electrolysis of fused halides [5].

Lanthanum Identification

Atomic number 57 [1]
CAS number 7439-91-0 [1]
Position in the periodic table Group Period Block
  Lanthanides [1] 6 [1] d [1]

Properties and Characteristics of Lanthanum

General Properties

Atomic mass 138.905 amu [1]
Relative atomic mass 138.905 [1]

Physical Properties

Color Silvery-white [1, 5]
Melting point/freezing point 920 °C, 1688 °F [1]
Boiling point 3464 °C, 6267 °F [1]
Density 6.15 g cm-3 [1]
State of matter at room temperature (solid/liquid/gas) Solid [1, 5]
Hardness
– Brinell 363 MPa [6]
– Mohs 2.5 [6]
– Vickers 491 MPa [6]
Electrical conductivity 1.6X106 S/m [6]
Thermal (heat) conductivity 13 W/(m K) [6]
Specific heat 195 J kg-1 K-1 [1]
Bulk modulus 27.9 GPa [1]
Shear modulus 14.3 GPa [1]
Young’s modulus 36.6 GPa [1]
Vapor pressure
– Temperature (K) 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
– Pressure (Pa) 5.09X 10-8 2.02X 10-5 1.81X 10-3 5.96X 10-2 0.976 9.61 64.7

Chemical Properties

Oxidation states 3 [1]
Isotopes Isotope Mass Abundance Half-life Mode of decay
  138La 137.907 0.09 1.06 X 1011 y
  139La 138.906 99.91

Atomic Data of Lanthanum (Element 57)

Valence electrons 3 [6]
Quantum numbers
– n 4 [7]
– ℓ 3 [7]
– mℓ -3 [7]
– ms +1/2 [7]
Electron configuration (noble gas configuration) [Xe] 5d16s2 [1]
Atomic structure
– Number of electrons 57 [5]
– Number of neutrons 82 [5]
– Number of protons 57 [5]
Radius of Atom
– Atomic radius 2.43 Å [1]
– Covalent radius 1.94 Å [1]
Electronegativity (Pauling-scale) 1.10 [1]
Electron affinity 45.35 kJ mol-1 [1]
Ionization energy (kJ mol-1) 1st 2nd 3rd 4th 5th 6th 7th 8th
  538.089 1067.031 1850.328 4819.44 5943.5

Lanthanum Electron Configuration (Bohr Model)

What is Lanthanum Used for

Although lanthanum metal is not commercially used, its alloys may have some uses [1]:

  • An alloy of lanthanum and nickel is used for hydrogen storage in hydrogen-fueled vehicles [1]. It is used in large amounts in the anode (positively charged electrode) of NiMH (nickel metal hydride) batteries that are found in hybrid cars [1, 5].
  • Lanthanum is a constituent element in misch metal (an alloy of rare earth metals) that is used in flints for producing igniting sparks in cigarette lighters [1].
  • Compounds with lanthanum are extensively used in cinema projection, studio lighting, and other carbon lighting applications [1].
  • Lanthanum (III) oxide (La2O3) is used in producing high-quality optical glasses, telescope and camera lenses because it has low dispersion, high refractive index, and it imparts high alkali resistance [1, 5], producing a clear, sharp image.
  • It is used as a catalyst in petroleum industries for cracking the long chain hydrocarbons [5].
  • Ionic lanthanum (La3+) is used as a tracer and marker of Ca2+ spikes in blood, and studies have shown that radioactive lanthanum and its compounds may be used in treating cancer [1].
  • Lanthanum carbonate (fosrenol) is useful for reducing phosphate levels in people affected by kidney disease [5].

Possible Health Effects

Lanthanum and its compounds, although not known to play any biological role in humans, can be a little or moderately toxic and should be handled with caution and proper protection [1].

Interesting Facts

  • The element rapidly oxidizes in air and is easily burned when ignited [1].
  • It is sometimes visually represented with an image of a camera lens in reference to its use in cameras [1].

How much does Lanthanum Cost

The price of 100 grams of pure lanthanum is around $800 while its price in bulk ranges between $6,000 and $6,500 [5, 8].

References

  1. http://www.rsc.org/periodic-table/element/57/lanthanum
  2. https://pubchem.ncbi.nlm.nih.gov/compound/lanthanum#section=Top
  3. https://education.jlab.org/itselemental/ele057.html
  4. https://www.webelements.com/lanthanum/isotopes.html
  5. https://www.chemicool.com/elements/lanthanum.html
  6. http://periodictable.com/Elements/057/data.html
  7. http://chemistry-reference.com/q_elements.asp?language=en&Symbol=La
  8. https://hobart.k12.in.us/ksms/PeriodicTable/lanthanum.htm

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