Lanthanum (La)
Lanthanum is element 57, a lanthanide in period 6 of the periodic table. At room temperature it is a solid.
Electron configuration [Xe] 5d1 6s2
Electrons per shell 2, 8, 18, 18, 9, 2
Lanthanum data
| Atomic number | 57 |
|---|---|
| Symbol | La |
| Atomic mass | 138.905 u |
| Category | Lanthanide |
| Group | — (f-block) |
| Period | 6 |
| Block | f |
| State at 25 °C | solid |
| Melting point | 1193 K (919.9 °C) |
| Boiling point | 3737 K (3463.9 °C) |
| Density | 6.146 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| Atomic radius | 169 pm |
| 1st ionization energy | 538 kJ/mol |
| Electron affinity | -48 kJ/mol |
| Oxidation states | +2, +3 |
| Common ion charge | 3+ |
| Discovered | 1839 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through lanthanum’s configuration and its ions →
Where lanthanum sits
Lanthanum belongs to the lanthanides. Its Pauling electronegativity of 1.1 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Lanthanum FAQ
What is the electron configuration of lanthanum?
Lanthanum (Z = 57) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2. In noble-gas shorthand that is [Xe] 5d1 6s2. This is an exception to the simple Aufbau prediction (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f1 5s2 5p6 6s2); a half-filled or filled subshell lowers the energy.
How many valence electrons does lanthanum have?
3 (2 outer s + 1 d electrons; 2 in the outermost shell).
What is the atomic mass of lanthanum?
The standard atomic weight of lanthanum is 138.905 u, so one mole weighs 138.905 g.
Is lanthanum a metal?
Yes. Lanthanum is a lanthanide.
What is the charge of a lanthanum ion?
Lanthanum most commonly forms La3+.