Lanthanum (La) - Element 57 | Properties & Electron Configuration
What is Lanthanum?
Lanthanum (La) is element 57, a lanthanide in period 6. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s².
| Atomic Number | 57 |
| Symbol | La |
| Atomic Mass | 138.91 u |
| Category | Lanthanide |
| Period | 6 |
| Group | N/A (f-block) |
| Block | f |
| Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s² |
| Short Config | [Xe] 5d¹ 6s² |
| Electronegativity | 1.1 |
| Atomic Radius | 195 pm |
| Ionization Energy | 538 kJ/mol |
| Electron Affinity | 48 kJ/mol |
| Phase (STP) | Solid |
Electron Configuration
The full electron configuration of Lanthanum is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s². In noble gas shorthand, this is written as [Xe] 5d¹ 6s².
Lanthanum is a f-block element, period 6.
Periodic Trends
Electronegativity: Lanthanum has a Pauling electronegativity of 1.1.
Atomic Radius: 195 pm. Across period 6, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 538 kJ/mol. Ionization energy generally increases across a period and decreases down a group.
View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.
Explore Lanthanum on the Interactive Periodic Table