Lanthanum (La)
Lanthanum
Lanthanum (La) is a lanthanide in period 6. Its relative atomic mass is 138.91 and the molar mass of the atom is 138.91 g/mol.
Atomic number 57
Atomic mass 138.91
Molar mass 138.91 g/mol
Category Lanthanide Solid
Properties of lanthanum
| Atomic number | 57 |
|---|---|
| Symbol | La |
| Latin name | Lanthanum |
| Relative atomic mass | 138.91 |
| Molar mass | 138.91 g/mol |
| Group, period, block | —, 6, f |
| Category | Lanthanide |
| State at 20 °C | Solid |
| Electron configuration | [Xe] 5d¹ 6s² |
| Electronegativity (Pauling) | 1.1 |
| Atomic radius | 195 pm |
Electron configuration of lanthanum
Electrons per shell
K2L8M18N18O9P2
Full notation
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²
Noble-gas notation
57 protons · 57 electrons[Xe] 5d¹ 6s²
Formula and compounds of lanthanum
Simple substanceLalanthanumMolar mass of La: 138.91 g/mol
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Frequently asked questions
The relative atomic mass of lanthanum is 138.91, so the molar mass of the atom is 138.91 g/mol.
Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s². Noble-gas notation: [Xe] 5d¹ 6s².