Lanthanum (symbol La, atomic number 57) is the first lanthanide, used in camera lenses and hybrid-car batteries. It is classified as a lanthanide and sits in the lanthanide series (f-block), period 6 of the periodic table.
Overview
Lanthanum is the chemical element with atomic number 57 and the symbol La. With a standard atomic weight of 138.91, it is a lanthanide. In the periodic table it occupies the lanthanide series (f-block) and period 6, and under standard conditions it is normally a solid. Lanthanum is the first lanthanide, used in camera lenses and hybrid-car batteries.
Atomic structure
An atom of Lanthanum has 57 protons in its nucleus and, when neutral, 57 electrons arranged in the configuration [Xe] 5d1 6s2. Its standard atomic weight of 138.91 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Lanthanum was discovered in 1839 by Carl Gustaf Mosander. It follows Barium (Ba) and precedes Cerium (Ce) in order of atomic number.
| Atomic number | 57 |
|---|---|
| Symbol | La |
| Atomic mass | 138.91 |
| Category | Lanthanide |
| Group | — |
| Period | 6 |
| Electron configuration | [Xe] 5d1 6s2 |
| Phase at STP | Solid |
| Discovered | 1839 (Carl Gustaf Mosander) |