Lanthanum (La)
Lanthanide · f-block · period 6
Soft, silvery-white, ductile metal that tarnishes quickly.
Lanthanum (symbol La) is chemical element number 57, a lanthanide in the lanthanide series (f-block), period 6 of the periodic table. Its standard atomic weight is 138.91 and its electron configuration is [Xe] 5d1 6s2. At room temperature it is a solid. Its name is Greek for 'to lie hidden'.
Properties
| Atomic number | 57 |
|---|---|
| Atomic mass | 138.91 |
| Category | Lanthanide |
| Block | f-block |
| Group · Period | f-block series · 6 |
| Electron configuration | [Xe] 5d1 6s2 |
| Electrons per shell | 2, 8, 18, 18, 9, 2 |
| State at 25 °C | solid |
| Melting point | 1193 K |
| Boiling point | 3737 K |
| Density | 6.16 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1839 · Carl Gustaf Mosander |
Key facts about Lanthanum
- Its name is Greek for 'to lie hidden'.
- The head of the lanthanide (rare-earth) row.
- Lanthanum glass has a high refractive index and is prized for camera lenses.
- The 'mischmetal' in lighter flints is mostly lanthanum and cerium.
What Lanthanum is used for
Camera and telescope lenses, nickel-metal-hydride battery electrodes, catalysts for oil refining, lighter flints.
Where it sits in the periodic table
Lanthanum is in the lanthanide series, period 6, of the f-block. Its electron configuration [Xe] 5d1 6s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Lanthanum on the interactive table →
Lanthanum — frequently asked questions
What is Lanthanum used for?
Camera and telescope lenses, nickel-metal-hydride battery electrodes, catalysts for oil refining, lighter flints.
Is Lanthanum radioactive?
No. Lanthanum has at least one stable isotope and is not radioactive.
What is the electron configuration of Lanthanum?
Lanthanum has the electron configuration [Xe] 5d1 6s2, which is 2, 8, 18, 18, 9, 2 electrons per shell.
What group and period is Lanthanum in?
Lanthanum is in the lanthanide series (f-block), period 6, in the f-block. Its outer shell holds 2 electrons.
Who discovered Lanthanum?
Lanthanum was discovered in 1839 by Carl Gustaf Mosander.