Although the word "lanthanum" means "being hidden", it is more abundant than most metals. For example, it is three times more common than lead. This element was discovered in the mineral cerite in 1839. However, it took chemists almost another 100 years to find a way to purify it. Today, the main source of pure lanthanum is the mineral bastnasite. Lanthanum's applications range from its use in film studio lights and lens manufacturing to petroleum refining.
Summary of properties (Lai)
| Atomic weight | 138.90547(7) |
| Discoverer (year) | Mosander, Carl Gustav (1839) |
| Natural form | metallic solid (hexagonal) |
| Electron configuration | [Xe] 5d1 6s2 |
| Melting point (ºC) | 920 |
| Boiling point (ºC) | 3469 |
| Abundance in earth's crust (ppm) | 39 |
| Isotope (abundance) | 138La (0.090), 139La (99.910) |
| Density g/cm3 | 6.15 |
| Van der Waals radius (pm) | 243 |
| Covalent radius (pm) | 194 |
| Electronegativity (Pauling) | 1.1 |
| Vaporization enthalpy (kJ/mol) | 399.60 |
| Enthalpy of fusion (kJ/mol) | 6.20 |
| Specific heat capacity (J/g·K) at 25ºC and 1 atm | 0.20 |
| Thermal conductivity (W/cm·K) at 25ºC and 1 atm | 0.130 |
| Oxidation state | +3 |
| Electron affinity (eV) | 0.47 |
| 1st Ionization potential (eV) | 5.5769 |
