57138.91LaLanthanum
Lanthanum (La) — element 57lanthanide · period 6
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a lanthanide in period 6 of the periodic table (the f-block), with a standard atomic mass of 138.91 u. At room temperature (25 °C) lanthanum is a solid.
💡 Known for: Used in camera lenses, nickel–metal hydride batteries in hybrid cars and oil-refining catalysts.
# Lanthanum properties
| Symbol | La |
|---|---|
| Atomic number | 57 |
| Atomic mass | 138.91 u |
| Category | lanthanide |
| Group | — (f-block, no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 5d¹ 6s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s² |
| Electrons per shell | 2, 8, 18, 18, 9, 2 |
| Protons / electrons | 57 / 57 |
| State at 25 °C | solid |
| Melting point | 1193 K (919.9 °C, 1687.7 °F) |
| Boiling point | 3737 K (3463.8 °C, 6266.9 °F) |
| Density | 6.145 g/cm³ |
| Electronegativity (Pauling) | 1.1 |
| First ionization energy | 5.577 eV |
| Atomic radius | 195 pm |
| Discovered | 1839 |
# Electron configuration of lanthanum
The electron configuration of lanthanum is [Xe] 5d¹ 6s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s². Its 57 electrons fill 6 shells as 2, 8, 18, 18, 9, 2, so the outermost shell holds 2 electrons.
# Related elements
BaBariumprevious elementCeCeriumnext elementPrPraseodymiumlanthanideNdNeodymiumlanthanidePmPromethiumlanthanideSmSamariumlanthanideEuEuropiumlanthanideGdGadoliniumlanthanideTbTerbiumlanthanideDyDysprosiumlanthanide
# Lanthanum FAQ
What is the atomic number of lanthanum?
The atomic number of lanthanum is 57: every lanthanum atom has 57 protons in its nucleus. Its symbol is La.
What is the atomic mass of lanthanum?
The standard atomic mass of lanthanum is 138.91 u.
What is the electron configuration of lanthanum?
Lanthanum's electron configuration is [Xe] 5d¹ 6s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²), with 2, 8, 18, 18, 9, 2 electrons per shell.
Is lanthanum a metal?
Yes. Lanthanum is a lanthanide, one of the metals.
What is the melting point of lanthanum?
Lanthanum melts at 1193 K (919.9 °C, 1687.7 °F) and boils at 3737 K (3463.8 °C, 6266.9 °F).
What is lanthanum used for / known for?
Used in camera lenses, nickel–metal hydride batteries in hybrid cars and oil-refining catalysts.