Terbium
[Xe] 4f⁹ 6s² · 2 · 8 · 18 · 27 · 8 · 2
The lanthanide that supplies the green in trichromatic phosphors, and the champion of magnetostriction: a terbium-dysprosium-iron alloy visibly changes length in a magnetic field.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 65
- Atomic mass
- 158.925 а.е.м.
- Electron configuration
- [Xe] 4f⁹ 6s²
- Electrons per shell
- 2 · 8 · 18 · 27 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 6
- Electronegativity (Pauling)
- 1.2
- Electronegativity (Allen)
- 1.1
- Atomic radius
- 221 pm
- Covalent radius
- 194 pm
- Van der Waals radius
- 221 pm
- Ionisation energy 1
- 565.8 kJ/mol
- Ionisation energy 2
- 1 110 kJ/mol
- Ionisation energy 3
- 2 114 kJ/mol
- Ionisation energy 4
- 3 839 kJ/mol
- Electron affinity
- 50 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +1, +2, +3, +4
Physical properties
- State at 25 °C
- solid
- Density
- 8.23 g/cm³
- Melting point
- 1 629 K · 1 355.9 °C
- Boiling point
- 3 503 K · 3 229.9 °C
- Speed of sound
- 2 620 m/s
Thermal properties
- Heat of fusion
- 10.15 kJ/mol
- Heat of vaporisation
- 391 kJ/mol
- Specific heat capacity
- 0.182 J/(g·K)
- Thermal conductivity
- 11.1 W/(m·K)
Mechanical properties
- Young's modulus
- 55.7 GPa
- Shear modulus
- 22.1 GPa
- Bulk modulus
- 38.7 GPa
- Poisson ratio
- 0.26
- Mohs hardness
- no data
- Brinell hardness
- 677 MPa
Electrical and magnetic properties
- Electrical resistivity
- 1 150 nΩ·m
- Magnetic ordering
- ferromagnetic
- Curie point
- 221 K
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 360.55 pm · c = 569.66 pm
Abundance
- In the crust
- 1.2 mg/kg
- In the ocean
- 1.4·10⁻⁷ mg/L
- In the universe
- 0.05 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 159Tb | 100 % | stable | — |
Terbium-159 is the only stable isotope. Terbium-161 is under study for targeted radionuclide therapy.
Discovery
- Year of discovery
- 1843
- Discovered by
- Carl Gustaf Mosander
- Where
- Sweden
- Origin of the name
- after Ytterby, the village in Sweden
History
Mosander split the yttrium earth into three in 1843 and named the parts yttrium, erbium and terbium. The original names of erbium and terbium were later swapped after confusion.
Where it occurs
1.2 mg/kg of the crust — one of the rarest lanthanides. It is recovered from the ion-adsorption clays of southern China.
How it is produced
By separating heavy rare-earth concentrates; terbium is among the dearest lanthanides because there is so little of it.
Role in living things
No biological role.
Safety
Of low toxicity, like the other lanthanides. The powdered metal is pyrophoric and ignites readily in air, so it is stored under oil or in an inert atmosphere.
Uses
- Green phosphor in trichromatic lamps and displays
- Terfenol-D, a magnetostrictive alloy for sonar and precision actuators
- An additive to neodymium magnets to hold their properties when hot
- Magneto-optical solid-state storage
Curiosities
- Terbium, erbium, ytterbium and yttrium are all named after the single Swedish village of Ytterby.
- Terfenol-D lengthens by about a thousandth of itself in a strong field — enough for precision actuators.
- Terbium and dysprosium additions are the main reason electric vehicle magnets stay expensive.
- The green component of a fluorescent display image was terbium's work.