LA • Atomic Number 57
Lanthanum
Lanthanum is a silver-white, ductile, and highly reactive metal. It exists in three metallic modifications. After cerium, lanthanum is the most abundant of the rare earth metals and belongs to the group of light rare earth elements.
Its most important property is its pronounced ability to absorb hydrogen, making lanthanum a key component in nickel-metal hydride (NiMH) batteries.
Lanthanum was discovered in 1839 by the Swedish chemist and surgeon Carl Gustav Mosander. Like most rare earth elements, lanthanum was initially identified only in the form of its oxide, known as cerium dioxide (cerium(IV) oxide), and was not isolated as a pure metal until decades after its discovery.
The most economically significant minerals for lanthanum extraction are bastnäsite and monazite. It is primarily mined in China, the USA (Mountain Pass), and Australia (Mount Weld).
The economically most important minerals for lanthanum are bastnäsite and monazite. It is primarily extracted in China, the USA (Mountain Pass), and Australia (Mount Weld).
Lanthanum and cerium are the two most abundant light rare earth elements. They occur in large quantities in the most economically significant ores, bastnäsite and monazite.
In a typical bastnäsite deposit, cerium and lanthanum together can make up more than 50 percent of the total rare earth content. As a result, there is a significant and ongoing overproduction of cerium and lanthanum relative to market demand. This overproduction is a fundamental characteristic of the rare earth industry and is known as the “balance problem.”
After an elaborate separation of other accompanying lanthanides, the oxide is converted into lanthanum fluoride using hydrofluoric acid. This is then reduced with calcium, producing calcium fluoride and metallic lanthanum. Remaining calcium residues and impurities are removed through an additional vacuum remelting process.
The by far most important application of lanthanum is in nickel–metal hydride (NiMH) batteries, where lanthanum-containing alloys serve as the central component of the negative electrode (anode). Rechargeable NiMH batteries were formerly widespread in laptops, cameras and—most notably—in hybrid vehicles such as the Toyota Prius.
Together with cerium, lanthanum is an important constituent of mischmetal, an alloy of rare earth metals whose exact composition reflects the source ore, often with added iron.
Because of its pyrophoricity—fine shavings of the metal can ignite spontaneously in air from frictional heat—mischmetal is used in lighter flints.
Besides lighters, mischmetal is used as an ignition agent for combustible gases and explosive charges. It is found in gas igniters for household stoves, ovens, heaters and water heaters, in firework and pyrotechnic igniters, and in certain military and industrial applications as a primer or ignition charge.
Due to its high reactivity, mischmetal can also be used as a reducing agent in specific metallurgical processes to reduce oxides.
With Cobalt
The cobalt–lanthanum alloy LaCo₅ is used as a magnetic material. Lanthanum-doped barium titanate is employed in the production of thermistors (temperature-dependent resistors). In combination with cobalt, iron, manganese, strontium, and others, it serves as a cathode material for high-temperature solid oxide fuel cells (SOFC). “Impure” lanthanum-nickel (LaNi₅) is used as a hydrogen storage material in nickel-metal hydride batteries. As an additive, lanthanum is also found in coal arc lamps for studio lighting and film projectors (historical application).
With Titanium
An alloy metal composed of lanthanum and titanium is known to reduce chip length during machining processes, which facilitates easier processing of the metal.
In the medical field, this corrosion-resistant and easily sterilizable titanium–lanthanum alloy is used to manufacture surgical instruments. It is particularly suitable for surgical tools and devices due to its low allergy potential compared to other alloys.
As Lanthanum Oxide
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Used in the manufacture of optical glasses (lanthanum glass) with relatively high refractive index and low dispersion, ideal for camera lenses, telescope optics, and eyeglass lenses.
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Used in crystal glass and porcelain glazes, replacing more toxic lead compounds while improving chemical resistance (enhancing alkali resistance, making them dishwasher safe).
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Added as a catalyst additive to zeolites in fluid catalytic cracking during petroleum refining.
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Used in the production of ceramic capacitor materials and silicate-free glasses.
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Component in glass polishing agents.
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Used for manufacturing cathodes in electron tubes (including lanthanum borides).
As Lanthanum Carbonate:
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Used as a medication to reduce phosphate levels in dialysis patients (phosphate binder).
Lanthanum is considered to have low toxicity, and no toxic dose has been conclusively established. However, lanthanum powder is strongly corrosive because it readily reacts with moisture (e.g., skin moisture) to form basic lanthanum hydroxide (similar to calcium and strontium). The lethal dose for rats is approximately 720 mg.
| General Information | |
| Name, Symbol, Atomic Number | Lanthanum, La, 57 |
| Series | Transition metals |
| Groupe, Periode, Block | 3, 6, d |
| Appearance | silvery-white |
| CAS-Number | 7439-91-0 |
| Abundance in Earth's crust | 17ppm |
| Atomic Properties | |
| Atomic Mass | 138.9055 u |
| Atomic Radius | 195 pm |
| Covalent Radius | 207 pm |
| Electron Configuration | [Xe] 5d¹ 6s² |
| 1. Ionization Energy | 538.1 kJ/mol |
| 2. Ionization Energy | 1067 kJ/mol |
| 3. Ionization Energy | 1850 kJ/mol |
| 4. Ionization Energy | - |
| Physical Properties | |
| State of Matter | solid |
| Crystal Structure | Hexagonal |
| Density | 6.17 g/cm³ (at 20 °C) |
| Magnetism |
Paramagnetic (χm = 5.4 × 10⁻⁵) |
| Melting Point | 1193 K (920 °C) |
| Boiling Point | 3743 K (3470 °C) |
| Molar Volume | 22.39 * 10⁻⁶ m³/mol |
| Heat of Vaporization | 400 kJ/mol |
| Heat of Fusion | 6.2 kJ/mol |
| Electrical Conductivity | 1.626 * 10⁶ A/(V·m) |
| Thermal Conductivity | 13 W/(m*K) |
The silver-white metal is malleable and ductile. It exists in three metallic modifications.
Lanthanum is a reactive (non-noble) metal. In air, it quickly forms a white oxide layer, which further reacts to form a hydroxide in moist air.
Rare Earth Elements
