About

Lanthanum is a soft, ductile, silvery-white metal that gives its name to the lanthanide series of elements. Its name means 'to lie hidden' as it was difficult to separate from other rare earths. It is used to make high-refractive-index glass for high-quality camera lenses and telescopes. It is also a major component of the nickel-metal hydride (NiMH) batteries used in many hybrid cars.

Atomic Properties

Atomic Number57

Atomic Weight138.905 u

Neutrons (common)82

Electron Configuration[Xe] 5d¹ 6s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s²

Electrons per Shell2, 8, 18, 18, 9, 2

Electronegativity1.1

Electron Affinity48 kJ/mol

Oxidation States+3, +2

Covalent Radius195 pm

Ionic Radius103.2 pm

Periodic Table Position

Group3

Period6

BlockD

Chemical SeriesLanthanoids

Physical Properties

State at STPsolid

Appearancesilvery-white

Crystal Structurehcp

Magnetic Orderingparamagnetic

Speed of Sound2,475 m/s

Poisson Ratio0.28

Thermal Properties

Melting Point1,193 K

Boiling Point3,737 K

Thermal Expansion0 1/K

Thermal Conductivity13.4 W/(m·K)

Specific Heat0.195 J/(g·K)

Molar Heat27.1 J/(mol·K)

Heat of Fusion6.2 kJ/mol

Heat of Vaporization402.1 kJ/mol

Abundance

In Earth's Crust35 ppm

In Ocean0 ppm

In Solar System0.001 ppm

In Universe0.002 ppm

Discovery

Discovered byCarl Gustaf Mosander

Discovery Year1,839

Occurrenceprimordial

CAS Number7439-91-0

Electron Configuration

Energy

↿⇂

↿

Isotopes of Lanthanum

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
¹³⁸La	137.907110	0.0888%	103 Gy	Electron Capture, Beta Minus Decay
¹³⁹La	138.906350	99.911%	Stable	Stable

Interactive Visualization

Explore the 3D Bohr model of Lanthanum in our interactive viewer.

View 3D Model of Lanthanum