About

Terbium is a silvery-white rare-earth metal that is soft enough to be cut with a knife. It is used as the green phosphor in CRT screens and energy-efficient fluorescent lamps, emitting a brilliant lemon-yellow light. It's also a component of Terfenol-D, a magnetostrictive alloy that changes shape in a magnetic field, which is used in advanced naval sonar systems and sensors.

Atomic Properties

Atomic Number65

Atomic Weight158.925 u

Neutrons (common)94

Electron Configuration[Xe] 4f⁹ 6s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁹ 5s² 5p⁶ 6s²

Electrons per Shell2, 8, 18, 27, 8, 2

Electronegativity1.2

Electron Affinity110 kJ/mol

Oxidation States+3, +4

Covalent Radius161 pm

Ionic Radius92.3 pm

Periodic Table Position

Group3

Period6

BlockF

Chemical SeriesLanthanoids

Physical Properties

State at STPsolid

AppearanceSilvery-white metallic

Density at STP8.23 g/cm³

Crystal Structurehcp

Magnetic Orderingparamagnetic

Speed of Sound2,800 m/s

Poisson Ratio0.261

Thermal Properties

Melting Point1,629 K

Boiling Point3,503 K

Thermal Expansion0 1/K

Thermal Conductivity11.1 W/(m·K)

Specific Heat0.182 J/(g·K)

Molar Heat28.92 J/(mol·K)

Heat of Fusion10.8 kJ/mol

Heat of Vaporization293 kJ/mol

Abundance

In Earth's Crust1.2 ppm

In Ocean0 ppm

In Solar System0.047 ppm

In Universe0.001 ppm

Discovery

Discovered byCarl Gustaf Mosander

Discovery Year1,843

Occurrenceprimordial

CAS Number7440-27-9

Electron Configuration

Energy

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Isotopes of Terbium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
¹⁵⁹Tb	158.925350	100%	Stable	Stable

Interactive Visualization

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

View 3D Model of Terbium