Lanthanum (La)
Introduction
Lanthanum is a chemical element with atomic number 57 in the periodic table. In Earth’s crust, element 57 is mainly contained as the ferromagnetic metal cobalt (Co). This rare-earth metal is classified as a member of the lanthanides family of chemical elements.
As a transition metal, lanthanum is a chemical that has three allotropic forms, as well as three valence electrons in its outer electron shell.
Fact Box
Chemical and Physical Properties of Lanthanum
The symbol in the periodic table of elements: La
Atomic number: 57
Atomic weight (mass): 138.905 g.mol-1
Group number: 3 (Lanthanides)
Period: 6
Color: A silvery-white metal
Physical state: Solid at room temperature
Half-life: From less than a minute to 1.02×1011 years
Electronegativity according to Pauling: 1.1
Density: 6.18 g.cm-3 at 20°C
Melting point: 920°C, 1688°F, 1193 K
Boiling point: 3464°C, 6267°F, 3737 K
Van der Waals radius: 0.104 nm (+3)
Ionic radius: 1.16 (+3) Å
Isotopes: 38
Most characteristic isotope: 139La
Electronic shell: [Xe] 5d16s2
The energy of the first ionization: 539 kJ.mol-1
The energy of the second ionization: 1098 kJ.mol-1
The energy of the third ionization: 1840 kJ.mol-1
Discovery date: 1839 (by Carl Gustaf Mosander)
With the periodic table symbol La, atomic number 57, atomic mass of 138.905 g.mol-1, and electron configuration [Xe] 5d16s2, lanthanum is a soft, ductile, and malleable chemical element. In fact, this transition metal is so soft that it can be dented by any firm object.
This lanthanide exists in three allotropic forms: an α-phase (a double close-packed hexagonal structure), a β-phase (a face-centered cubic structure), and the γ-phase (body-centered cubic structure).
Lanthanum reaches its boiling point at 3464°C (6267°F or 3737 K), while its melting point is at 920°C (1688°F, 1193 K). This member of the lanthanides family of elements in the periodic table has an electronegativity of 1.1 according to Pauling, whereas the atomic radius according to van der Waals is 0.104 nm (+3) pm.
Lanthanum rapidly oxidizes and forms La2O3. Also, it tarnishes when exposed to air. When exposed to temperatures that range from 6K (−267 °C, or −449 °F) all the way to its melting point, this rare earth metal also displays paramagnetic properties.
Finally, the chemical with 57 protons in its nucleus displays a powerful magnetocaloric effect when combined with iron and silicon. In this combination, lanthanum forms cubic intermetallic compounds that can be expressed with the general chemical formula La(Fe1−xSix)13.
How Was Lanthanum Discovered?
In 1839, lanthanum was discovered as the oxide (lanthana) from cerium oxide (ceria) in Sweden. It was also one of the first elements that got classified in the lanthanides family.
Carl Gustaf Mosander’s Serendipitous Dicovery
That year, the Swedish chemist Carl Gustaf Mosander (1797 – 1858) was focused on the chemical analysis of a cerium salt sample at his workplace – the renowned Karolinska Institute. He was trying to detect the impurities that he was convinced do exist in the sample under his observation.
When he triggered the chemical reaction between cerium nitrate (Ce (NO3)3) and dilute nitric acid (HNO3), the result was a new substance composed of two new oxides. He labeled them lanthana (La2O3) and didymia.
While compiling his system of elements, Mendeleev had left a gap for the chemical labeled as ‘ekaboron’ that was yet to be discovered. The lanthanum oxide which Mosander discovered fitted perfectly in the intended place that was left waiting for the new element 57 in the periodic table.
How Did Lanthanum Get Its Name?
The name of the element 57 is derived from the Ancient Greek word ‘λανθάνειν’ (lanthanein), meaning to ‘lie hidden, to be concealed’. This owes to the insolubility of the lanthanum ions (and generally, of the ions of all lanthanides), which makes this rare-earth element difficult to be isolated from mineral ores.
Where Can You Find Lanthanum?
There are approximately 0.0018% of lanthanum in the Earth’s upper crust. This lanthanide has been found in the rare-earth minerals monazite and bastnaesite (also: bastnäsite), cerite, and xenotime mineral ores. The mineral monazite is mineral-rich in rare-earth elements, comprising around 25% lanthanum. Thus, this mineral ore is the most exploited natural source of lanthanum.
Lanthanum is extracted from the ores through the process of electromagnetic separation from previously crushed minerals. For commercial purposes, element 57 is acquired by crystallizing ammonium lanthanum nitrate rather than by its isolation from the mineral ores, a process that has proven to be laborious and expensive.
While the ion-exchange and solvent extraction processes of monazite sand ((Ce, La, Th, Nd, Y)PO4) produces lanthanum in its purest form, the metal form of lanthanum is typically obtained through electrolysis of fused anhydrous halides.
Lanthanum in Everyday Life
The pure, elemental form of lanthanum has no specific everyday uses. However, its alloys have a broad use:
- Lanthana (La2O3) improves the clarity of images seen on a camera due to its high refractive index when added to camera lens glass, color televisions, infrared absorbing glass, special optical glasses, and telescope lenses. It also improves light quality, so it’s widely used by the motion picture industry for studio lighting, projection, and energy-saving lamps;
- As a part of the mischmetal alloy (accounting for about 20%), this rare earth metal is used in the manufacturing of cigarette lighter flints;
- When added to metals like iron and steel, lanthanum makes them less brittle and more easily workable;
- Large amounts of lanthanum are used in the manufacturing process of nickel-metal hydride batteries that are used in hybrid cars;
- Hydrogen gas is safely stored in vessels made of a lanthanum-nickel alloy;
- One of the most significant uses of this element is the application of lanthanum-based rare-earth compounds as hosts for phosphors in fluorescent lighting, in X-ray detectors, in petroleum cracking catalysts, etc;
- When combined with iron and silicon, lanthanum is used in the manufacturing of magnetic refrigeration materials;
- As a substitute for radioactive thorium, lanthanum oxides are used in gas tungsten arc welding electrodes;
- Lanthanum-barium alloy has an application in the radiometric dating of various ores and rock formations;
- In the field of medicine, lanthanum is used as a tracer in radiological examinations, in order to diagnose calcium processing problems. The use of lanthanum in radiological diagnostics has been found to be quite convenient because lanthanum ions are able to block calcium channels in the body.
How Dangerous Is Lanthanum?
If inhaled, lanthanum dust may trigger a toxic reaction. Irritation of the lungs caused by lanthanum can result in pneumoconiosis.
What is Pneumoconiosis?
Pneumoconiosis is a chronic occupational lung disease that mostly affects workers who are exposed to dust particles during the manufacturing process. When the particles of fine mineral or chemical dust (such as silica, coal dust, or asbestos) enter the lungs, they trigger inflammation that blocks the airways and obstructs breathing.
What are the Symptoms of Pneumoconiosis?
The affected individuals may experience the following advert health effects:
- Shortness of breath;
- Excessive formation and built up of mucus in the lungs;
- Severe bouts of cough.
Environmental Effects of Lanthanum
Lanthanum has no known biological role for neither humans nor animals. However, this rare earth element, along with the other lanthanides, seem to be essential for some types of bacteria.
Namely, researchers from Pennsylvania State University came up with scientific evidence that might explain how the volcano bacteria species that thrive in volcanoes are able to survive. According to their findings, it might be possible that the volcano bacteria absorb the insoluble lanthanide ions from their surrounding.
Isotopes of Lanthanum
The atomic masses of the lanthanum isotopes range from 117 to 155. There are only two naturally occurring forms of lanthanum out of the 38 isotopes: lanthanum -139 (a stable isotope with a natural abundance of 99.9119%) and the radioactive lanthanum -138 (with a natural abundance of 0.0888%). With a half-life of 1.02 × 1011 years, the naturally occurring radioactive isotope 138La is also the most stable isotope of element 57.
Lanthanum-140 and lanthanum-139 are forms of this rare earth metal that are obtained as byproducts of uranium fission that occurs in the debris of nuclear test explosions.
| Nuclide
[n 1] |
Z | N | Isotopic mass (Da)
[n 2][n 3] |
Half-life
[n 4][n 5] |
Decay
mode [n 6] |
Daughter
isotope [n 7][n 8] |
Spin and
parity [n 9][n 5] |
Natural abundance (mole fraction) | |
| Excitation energy[n 5] | Normal proportion | Range of variation | |||||||
| 117La | 57 | 60 | 116.95007(43)# | 23.5(26) ms | β+ | 117Ba | (3/2+, 3/2−) | ||
| p | 116Ba | ||||||||
| 118La | 57 | 61 | 117.94673(32)# | 200# ms | β+ | 118Ba | |||
| 119La | 57 | 62 | 118.94099(43)# | 1# s | β+ | 119Ba | 11/2−# | ||
| 120La | 57 | 63 | 119.93807(54)# | 2.8(2) s | β+ | 120Ba | |||
| β+, p | 119Cs | ||||||||
| 121La | 57 | 64 | 120.93301(54)# | 5.3(2) s | β+ | 121Ba | 11/2−# | ||
| β+, p | 120Cs | ||||||||
| 122La | 57 | 65 | 121.93071(32)# | 8.6(5) s | β+ | 122Ba | |||
| β+, p | 121Cs | ||||||||
| 123La | 57 | 66 | 122.92624(21)# | 17(3) s | β+ | 123Ba | 11/2−# | ||
| 124La | 57 | 67 | 123.92457(6) | 29.21(17) s | β+ | 124Ba | (7−, 8−) | ||
| 125La | 57 | 68 | 124.920816(28) | 64.8(12) s | β+ | 125Ba | (11/2−) | ||
| 126La | 57 | 69 | 125.91951(10) | 54(2) s | β+ | 126Ba | (5)(+#) | ||
| 127La | 57 | 70 | 126.916375(28) | 5.1(1) min | β+ | 127Ba | (11/2−) | ||
| 128La | 57 | 71 | 127.91559(6) | 5.18(14) min | β+ | 128Ba | (5+) | ||
| 129La | 57 | 72 | 128.912693(22) | 11.6(2) min | β+ | 129Ba | 3/2+ | ||
| 130La | 57 | 73 | 129.912369(28) | 8.7(1) min | β+ | 130Ba | 3(+) | ||
| 131La | 57 | 74 | 130.91007(3) | 59(2) min | β+ | 131Ba | 3/2+ | ||
| 132La | 57 | 75 | 131.91010(4) | 4.8(2) h | β+ | 132Ba | 2− | ||
| 133La | 57 | 76 | 132.90822(3) | 3.912(8) h | β+ | 133Ba | 5/2+ | ||
| 134La | 57 | 77 | 133.908514(21) | 6.45(16) min | β+ | 134Ba | 1+ | ||
| 135La | 57 | 78 | 134.906977(11) | 19.5(2) h | β+ | 135Ba | 5/2+ | ||
| 136La | 57 | 79 | 135.90764(6) | 9.87(3) min | β+ | 136Ba | 1+ | ||
| 137La | 57 | 80 | 136.906494(14) | 6(2)×104 y | EC | 137Ba | 7/2+ | ||
| 138La[n 10] | 57 | 81 | 137.907112(4) | 1.02(1)×1011 y | β+ (66.4%) | 138Ba | 5+ | 9.0(1)×10−4 | |
| β− (33.6%) | 138Ce | ||||||||
| 139La[n 11] | 57 | 82 | 138.9063533(26) | Stable | 7/2+ | 0.99910(1) | |||
| 140La[n 11] | 57 | 83 | 139.9094776(26) | 1.6781(3) d | β− | 140Ce | 3− | ||
| 141La | 57 | 84 | 140.910962(5) | 3.92(3) h | β− | 141Ce | (7/2+) | ||
| 142La | 57 | 85 | 141.914079(6) | 91.1(5) min | β− | 142Ce | 2− | ||
| 143La | 57 | 86 | 142.916063(17) | 14.2(1) min | β− | 143Ce | (7/2)+ | ||
| 144La | 57 | 87 | 143.91960(5) | 40.8(4) s | β− | 144Ce | (3−) | ||
| 145La | 57 | 88 | 144.92165(10) | 24.8(20) s | β− | 145Ce | (5/2+) | ||
| 146La | 57 | 89 | 145.92579(8) | 6.27(10) s | β− (99.99%) | 146Ce | 2− | ||
| β−, n (.007%) | 145Ce | ||||||||
| 147La | 57 | 90 | 146.92824(5) | 4.015(8) s | β− (99.96%) | 147Ce | (5/2+) | ||
| β−, n (.04%) | 146Ce | ||||||||
| 148La | 57 | 91 | 147.93223(6) | 1.26(8) s | β− (99.85%) | 148Ce | (2−) | ||
| β−, n (.15%) | 147Ce | ||||||||
| 149La | 57 | 92 | 148.93473(34)# | 1.05(3) s | β− (98.6%) | 149Ce | 5/2+# | ||
| β−, n (1.4%) | 148Ce | ||||||||
| 150La | 57 | 93 | 149.93877(43)# | 510(30) ms | β− (97.3%) | 150Ce | (3+) | ||
| β−, n (2.7%) | 149Ce | ||||||||
| 151La | 57 | 94 | 150.94172(43)# | 300# ms [>300 ns] | β− | 151Ce | 5/2+# | ||
| 152La | 57 | 95 | 151.94625(43)# | 200# ms [>300 ns] | β− | 152Ce | |||
| 153La | 57 | 96 | 152.94962(64)# | 150# ms [>300 ns] | β− | 153Ce | 5/2+# | ||
| 154La | 57 | 97 | 153.95450(64)# | 100# ms | β− | 154Ce | |||
| 155La | 57 | 98 | 154.95835(86)# | 60# ms | β− | 155Ce | 5/2+# | ||
Source: Wikipedia
List of Lanthanum Compounds
This transition metal is one of the most reactive lanthanides. It reacts slowly with H2O to form lanthanum hydroxide compounds, but it gets diluted more rapidly in acids. Hydrofluoric acid (HF) is an exception because it coats the surface of the metal with a protective fluoride layer (LaF3).
Lanthanum typically adopts the oxidation state of +3. It binds to carbonates and phosphates easily. In a chemical reaction with halogens at room temperature, this member of the lanthanide series forms trihalides.
The most common lanthanum compounds include:
- Lanthanum(III) Nitrate
- Lanthanum Iodate
- Lanthanum Fluoride
- Lanthanum Sulfate
- Lanthanum(III) Phosphate
- Lanthanum Carbonate
- Lanthanum Bromate
- Lanthanum Hydrogen Carbonate
- Lanthanum Oxide
- Lanthanum Sulfite
- Lanthanum Dihydrogen Phosphate
- Lanthanum Hydrogen Sulfate
- Lanthanum Hydrogen Phosphate
- Lanthanum Bromate Nonahydrate
- Lanthanum Selenate
- Lanthanum Silver
- Lanthanum Telluride
- Lanthanum Chlorate
- Lanthanum Perchlorate
- Lanthanum Arsenate
- Lanthanum Hydroxide
- Lanthanum Thiosulfate
- Lanthanum Hypochlorite
- Lanthanum Mercury
- Lanthanum Sulfide
- Lanthanum Peroxide
- Lanthanum Cadmium
- Lanthanum Arsenide
- Lanthanum Tallium
- Lanthanum Aluminum
- Lanthanum Nitrite
5 Interesting Facts and Explanations
-
- The lanthanides group of elements comprises 15 chemicals with atomic numbers that range from 57 through 71, located between lanthanum and lutetium. Sometimes, the elements scandium (with atomic number 21) and yttrium (with atomic number 39) are included as members of the lanthanides family of the periodic table because they were discovered at the same time with the lanthanide elements in rare minerals and isolated as rare earth oxides. Lanthanides are, in fact, the transition metals that follow lanthanum on the periodic table (hence their name).
- Only the elements from 58 to 71 are considered to be real lanthanides due to their ability to fill the 4f electron subshell of the atom. Even though this is not the case with element 57 (lanthanum), it’s still classified in this group since it expresses similar chemical properties with the aforementioned lanthanides.
- The Methylacidiphilum fumariolicum is a type of volcanic bacteria that cannot live without lanthanum to boost the methanol dehydrogenase enzyme, which is of vital importance for its survival.
- Mischmetal literally means ‘mixed metal’ in German. It’s a compound that is usually made up of 50% cerium, 25% lanthanum, 18% neodymium, 5% praseodymium, and 2% other rare-earth metals.
- After the element europium, lanthanum is the second most reactive rare earth metal.