La
Lanthanum
Element 57 · Lanthanide
Lanthanum (La)
Lanthanum is a soft, silvery rare-earth metal that gives its name to the lanthanide series.
- Lanthanide
- Period 6
- f-block series
- f-block
- solid at room temperature
Key properties
- Atomic mass
- 138.9055
- u
- Electron configuration
- [Xe] 5d1 6s2
- Melting point
- 917.9 °C
- 1,191 K
- Boiling point
- 3,463.9 °C
- 3,737 K
- Density
- 6.15 g/cm³
- Electronegativity
- 1.1
- Pauling
- Atomic radius
- 240 pm
- van der Waals
- 1st ionisation energy
- 5.577 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about lanthanum
- 01
A Toyota Prius battery contains several kilograms of lanthanum.
- 02
Lanthanum oxide makes camera lens glass with a high refractive index.
- 03
It is used in the carbon arc lamps of film projectors and studio lights.
Applications
What is lanthanum used for?
- Nickel–metal hydride batteries
- Camera and telescope lenses
- Oil-refining catalysts
- Hydrogen storage
History
Discovery & name origin
Discovered by
Year
Where
Sweden
Name origin
Greek lanthanein, “to lie hidden” — it hid inside cerium minerals.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 57
- Atomic mass
- 138.9055 u
- Group
- Lanthanides (3)
- Period
- 6
- Block
- f-block
- Electron configuration
- [Xe] 5d1 6s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d1
- Electrons per shell
- 2, 8, 18, 18, 9, 2
- Electronegativity (Pauling)
- 1.1
- Electron affinity
- 0.5 eV
- Atomic radius (van der Waals)
- 240 pm
- Stable isotopes
- 1
Oxidation states
Highlighted: common oxidation states (+3).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st538.1
- 2nd1,067
- 3rd1,850.3
- 4th4,819
- 5th5,940
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 1,191 K · 917.9 °C · 1,684.1 °F
- Boiling point
- 3,737 K · 3,463.9 °C · 6,266.9 °F
- Density
- 6.15 g/cm³
- Molar heat capacity
- 27.11 J/(mol·K)
- Appearance
- Silvery white
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Lanthanum questions
What is La on the periodic table?
La is the symbol for lanthanum, element 57 on the periodic table. It sits in period 6, in the f-block, in the lanthanide category, and has an atomic mass of 138.9055.
What is the atomic number of lanthanum?
Lanthanum has atomic number 57, so every lanthanum atom has 57 protons in its nucleus. Its symbol is La and its atomic mass is 138.9055.
Who discovered lanthanum?
Lanthanum was discovered by Carl Gustaf Mosander in 1839 (Sweden). The name comes from Greek lanthanein, “to lie hidden” — it hid inside cerium minerals.
What is lanthanum used for?
Lanthanum is used for: nickel–metal hydride batteries; camera and telescope lenses; oil-refining catalysts; hydrogen storage.
Is lanthanum a metal?
Yes. Lanthanum is a lanthanide, one of the metallic elements.
What is the electron configuration of lanthanum?
The electron configuration of lanthanum is [Xe] 5d1 6s2. Its 57 electrons are arranged in shells as 2, 8, 18, 18, 9, 2.