Lanthanum (La) – element 57
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a lanthanide in group 3 (lanthanides), period 6 of the periodic table (f-block), and is a solid at room temperature.
Lanthanum (La) has atomic number 57, atomic mass 138.91 u and electron configuration [Xe] 5d16s2.
Lanthanum facts
| Symbol | La |
|---|---|
| Atomic number | 57 |
| Atomic mass | 138.91 u (g/mol) |
| Category | lanthanide |
| Group | group 3 (lanthanides) |
| Period | 6 |
| Block | f-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1 |
| Noble-gas notation | [Xe] 5d16s2 |
| Electrons per shell | 2, 8, 18, 18, 9, 2 |
Bohr model and shells
Lanthanum has 57 electrons in 6 shells: 2, 8, 18, 18, 9, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 1193 K (919.9 °C) |
|---|---|
| Boiling point | 3737 K (3463.8 °C) |
| Density | 6.162 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| Electron affinity | 53 kJ/mol |
| Ionization energies | 538.1, 1067, 1850.3 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 27.11 J/(mol·K) |
| Discovered by | Carl Gustaf Mosander |
Use the atomic mass in the molar mass calculator for any formula containing La.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of lanthanum?
The atomic mass of lanthanum is 138.91 u, so one mole of lanthanum atoms weighs 138.91 g.
What is the electron configuration of lanthanum?
Lanthanum has 57 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 5d¹, or [Xe] 5d¹⁶s² in noble-gas notation. Electrons per shell: 2, 8, 18, 18, 9, 2.
Is lanthanum a metal?
Yes. Lanthanum is a lanthanide.
Where is lanthanum on the periodic table?
Lanthanum is in group 3 (lanthanides), period 6, in the f-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.