Lanthanum (La)
(From the Greek word lanthanein, to line hidden) Silvery metallic element belonging to group 3 of the periodic table and oft considered to be one of the lanthanoids. Found in some rare-earth minerals. Twenty-five natural isotopes exist. La-139 which is stable, and La-138 which has a half-life of 10^10 to 10^15 years. The other twenty-three isotopes are radioactive. It resembles the lanthanoids chemically. Lanthanum has a low to moderate level of toxicity, and should be handled with care. Discovered in 1839 by C.G. Mosander.
| Atomic Number | 57 |
|---|---|
| Atomic Weight | 138.90547 |
| Mass Number | 139 |
| Group | 3 |
|---|---|
| Period | 6 |
| Block | d |
| Protons | 57 p+ |
|---|---|
| Neutrons | 82 n0 |
| Electrons | 57 e- |
Properties
| Atomic Radius | 195 pm
|
|---|---|
| Atomic Volume | 22.5 cm³/mol
|
| Covalent Radius | 180 pm
|
| Metallic Radius | 169 pm
|
| Ionic Radius | 103.2 pm
|
| Crystal Radius | 117.19999999999999 pm
|
| Van der Waals radius |
243.00000000000003 pm
|
| Density | 6.15 g/cm³
|
| Boiling Point | 3,730 K
|
| Melting Point | 1,194 K
|
| Electrons per shell | 2, 8, 18, 18, 9, 2 |
| Electronegativity |
1.1
|
| Electrophilicity | 0.894990101872 eV/particle
|
| Proton Affinity | 1,013 kJ/mol
|
| Electron Affinity | 0.47 eV/particle
|
| Ionization Potential | 5.5769 eV/particle
|
| Heat of Vaporization | 402 kJ/mol
|
| Heat of Fusion | 8.5 kJ/mol
|
| Heat of Formation | 431 kJ/mol
|
| Molar Heat Capacity | 27.11 J/(mol K)
|
| Specific Heat Capacity | 0.195 J/(g⋅K)
|
| Thermal Conductivity | 13.4 W/(m K)
|
| Gas Basicity | 991.9 kJ/mol
|
| Dipole Polarizability | 215 a₀
|
| C6 Dispersion Coefficient | |
| Oxidation States | 2, 3 |
| Color | Silver
|
| Crystal Structure | Simple Hexagonal (HEX) |
| Lattice Constant | 3.75 Å
|
| Bulk Modulus | |
| Electrical Resistivity | |
| Electron Configuration | [Xe] 5d1 6s2 |
| Magnetic Ordering | |
| Magnetic Susceptibility | |
| Phase | Solid |
| Poisson Ratio | |
| Shear Modulus | |
| Young's Modulus | |
| Allotropes | |
| Alternate Names | |
| Adiabatic Index | |
| Appearance | |
| Electric Conductivity | |
| Critical Pressure | |
| Critical Temperature | |
| Curie Point | |
| Electrical | |
| Hardness | |
| Magnetic Susceptibility | |
| Magnetic | |
| Neel Point | |
| Neutron Cross Section | |
| Neutron Mass Absorption | |
| Gas Phase | |
| Quantum Numbers | |
| Refractive Index | |
| Space Group | |
| Speed of Sound | |
| Superconducting Point | |
| Thermal Expansion | |
| Valence Electrons | |
| Classification | |
| Category | Lanthanides, Lanthanides |
| CAS Group | IIIA |
| IUPAC Group | IIIB |
| Glawe Number | 32 |
| Mendeleev Number | 13 |
| Pettifor Number | 33 |
| Geochemical Class | rare earth & related |
| Goldschmidt Class | litophile |
| Radioactivity | |
| Radioactive | No |
| Decay Mode | |
| Half-Life | |
| Lifetime | |
| Abundance | |
| Abundance in Earth's crust | 39 mg/kg
|
| Abundance in Oceans | 0.0000034 mg/L
|
| Abundance in Human Body | |
| Abundance in Meteor | |
| Abundance in Sun | |
| Abundance in Universe | 2×10-7% |
Isotopes of Lanthanum
Stable Isotopes
138La 139La
Unstable Isotopes
117La 118La 119La 120La 121La 122La 123La 124La 125La 126La 127La 128La 129La 130La 131La 132La 133La 134La 135La 136La 137La 140La 141La 142La 143La 144La 145La 146La 147La 148La 149La 150La 151La 152La 153La 154La 155La
History
Lanthanum was discovered in 1839 by Swedish chemist Carl Gustav Mosander. He partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the resulting solution, he obtained a pale brick colored oxide of the new rare earth. Lanthanum was isolated in relatively pure form in 1923. From the Greek word lanthanein, to lie hidden
| Discoverers | Carl Mosander |
|---|---|
| Discovery Location | Sweden |
| Discovery Year | 1839 |
| Name Origin | Greek: lanthanein (to be hidden). |
Lanthanum and its compounds are considered to be moderately toxic
Lanthanum is the most reactive of the rare earth metals
Uses
Lanthanum is used in large quantities in batteries for hybrid automobiles. It is also used to make night vision goggles. Small amounts of lanthanum, as an additive, can be used to produce nodular cast iron. Lanthanum carbonate is used to reduce blood levels of phosphate in patients with kidney disease. It is used in the electodes of high-intensity, carbon-arc lights. Also used in the production of high-grade europium metal. Because it gives glass refractive properties, it is used in expensive camera lenses.
Sources
Found with rare earths in monazite and bastnasite. Monazite sand typicall contains 25% lanthanum.