What is Lanthanum
Lanthanum (pronunciation: LAN-the-nem)  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].
Where can Lanthanum be Found
The element naturally occurs in bastnaesite and monazite, making up 38% and 25% of the rare-earth minerals respectively . Isolation of lanthanum from these minerals involves solvent extraction and ion-exchange separation techniques . The metal can be produced through calcium reduction of anhydrous fluoride . 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 .
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 .
Who discovered it: The Swedish chemist Carl Gustaf Mosander is credited with the discovery of lanthanum .
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 . He took powdered cerium nitrate and treated it with dilute nitric acid . 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 . The pale brick-colored oxide obtained was given the name lanthana [3, 5].
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 . In 1923, pure lanthanum was obtained by Kremers and Stevens through electrolysis of fused halides .
|Atomic number||57 |
|CAS number||7439-91-0 |
|Position in the periodic table||Group||Period||Block|
|Lanthanides ||6 ||d |
Properties and Characteristics of Lanthanum
|Atomic mass||138.905 amu |
|Relative atomic mass||138.905 |
|Color||Silvery-white [1, 5]|
|Melting point/freezing point||920 °C, 1688 °F |
|Boiling point||3464 °C, 6267 °F |
|Density||6.15 g cm-3 |
|State of matter at room temperature (solid/liquid/gas)||Solid [1, 5]|
|– Brinell||363 MPa |
|– Mohs||2.5 |
|– Vickers||491 MPa |
|Electrical conductivity||1.6X106 S/m |
|Thermal (heat) conductivity||13 W/(m K) |
|Specific heat||195 J kg-1 K-1 |
|Bulk modulus||27.9 GPa |
|Shear modulus||14.3 GPa |
|Young’s modulus||36.6 GPa |
|– 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|
|Oxidation state/Oxidation number||+2, +3 |
|Isotopes||Isotope||Mass||Abundance||Half-life||Mode of decay|
|138La||137.907||0.09||1.06 X 1011 y||–|
Atomic Data of Lanthanum (Element 57)
|Valence electrons||3 |
|– n||4 |
|– ℓ||3 |
|– mℓ||-3 |
|– ms||+1/2 |
|Electron configuration (noble gas configuration)||[Xe] 5d16s2 |
|– Number of electrons||57 |
|– Number of neutrons||82 |
|– Number of protons||57 |
|Radius of Atom|
|– Atomic radius||2.43 Å |
|– Covalent radius||1.94 Å |
|Electronegativity (Pauling-scale)||1.10 |
|Electron affinity||45.35 kJ mol-1 |
|Ionization energy (kJ mol-1)||1st||2nd||3rd||4th||5th||6th||7th||8th|
What is Lanthanum Used for
Although lanthanum metal is not commercially used, its alloys may have some uses :
- An alloy of lanthanum and nickel is used for hydrogen storage in hydrogen-fueled vehicles . 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 .
- Compounds with lanthanum are extensively used in cinema projection, studio lighting, and other carbon lighting applications .
- 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 .
- 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 .
- Lanthanum carbonate (fosrenol) is useful for reducing phosphate levels in people affected by kidney disease .
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 .
- The element rapidly oxidizes in air and is easily burned when ignited .
- It is sometimes visually represented with an image of a camera lens in reference to its use in cameras .
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].
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