Terbium Tb (Element 65) of Periodic Table

65 Tb (Terbium)

It is a soft, malleable, ductile, silver-gray metal.
It is stable in air, but it is slowly oxidised and it reacts with cold water.

Identity
CAS Number: CAS7440-27-9
CID Number:  CID23958

Basic Properties of Terbium

Pronunciation:  Tur-bee-am
Appearance:  Silvery white
Mass Number:  158
Standard Atomic weight:  158.925 g/mol
Atomic number (Z):  65
Electrons: 65
Protons:  65
Neutrons:  93
Period:  6
Block:  f
Element category:  Lanthanide
Electrons per shell:  K2, L8, M18, N27, O8, P2
Electron configuration:  1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶4f⁹6s² 

Thermal Properties of Terbium

Phase:  Solid
Melting point:  1629 K (1356 ^oC, 2473 ^oF)
Boiling point:   3396 K (3123 ^oC, 5653 ^oF)
Fusion heat:  10.15 kJ/mol
Vaporization heat:  391 kJ/mol
Molar heat capacity:  28.91 J/(mol.K)
Thermal expansion: α, poly: 10.3 μm/(m∙K)
Thermal conductivity:  11.1 W/(m∙K)
Neel Point:  230 K

Electrical properties of Terbium

Electrical conductivity: 8.3×10⁶ S/m
a Electrical resistivity: α, poly: 1.150 μΩ∙m
a Electrical type:  Conductor

Magnetic Properties of Terbium

Magnetic type:  Paramagnetic
Curie point:  222 K
Magnetic susceptibility (x_mol):  +146,000×10^-6 cm³/mol
Volume magnetic susceptibility:  0.1117784
Mass magnetic susceptibility:  13600×10^-9 m³/kg
Molar magnetic susceptibility:  2161.385×10^-9 m³/mol

Physical Properties of Terbium

Density:  8.23 g/cm³ (In solid)  7.65 g/cm³ (In Liquid)
Molar volume:  0.00001934 m³/mol
Young’s modulus:  α  form: 55.7 GPa
Shear modulus:  α  form: 22.1 GPa
Mohs Hardness:  2.33
Bulk modulus:  α  form: 38.7 GPa
Poisson ratio:  α  form: 0.261
Vicker hardness:  450-865 MPa
Brinell hardness:  675-1200 MPa
Sound Speed:  2620 m/s

Atomic Properties of Terbium

Oxidation states:  4, 3, 2, 1
Valence Electrons:  4f⁹ 6s²
Ion charge:  Tb³⁺
Ionization energies:  1st: 565.8 kJ.mol 2nd: 1110 kJ/mol 3rd: 2114 kJ/mol
Ionic radius:   92.3 pm
Atomic radius:  221 pm (Van der Waals)
Covalent radius:  194±5 pm
Filling Orbital:  4f⁹
Crystal structure:  Hexagonal close-packed
Lattice angles:  π/2, π/2, π/3
Lattice constant:  360.0, 360.0, 569.39 pm
Grid parameters:  a=3.600 Å, c=5.694 Å
Attitude c/a:  1.582
Space Group Name:  P6₃/mmc
Space Group Number:  194

Reactivity of Terbium

Electronegativity:  pauling scale: 1.2
Valence:  +3
Electron affinity:  50 kJ/mol

Nuclear Properties of Terbium

Half Life:  Stable (Infinity)
Lifetime:  Stable (Infinity)
Quantum Number:  ⁶H_15/2
Neutron cross section (Brans):  23
Neutron Mass Absorption:  0.009
Isotopes:  157_Tb 158_Tb 159_Tb

Isotope	Abundance (%)	Atomic Mass g/mol	Half Life (t1/2)
157Tb	Syn	–	71 y
158Tb	Syn	–	180 y
159Tb	100	158.925	Stable

Chemical Reactions

The metal oxidation slowly in air and burns readily to form a mixed terbium (lll,lV) oxide:
8 Tb + 7 O₂ → 2 Tb₄O₇
Reacts slowly with cold water and quickly with hot water (form terbium hydroxide and hydrogen gas):
2 Tb + 6 H₂O → 2 Tb(OH)₃ + 3 H₂↑
The metal reacts with all Halogens to form Terbium (lll) halides:
2 Tb (s) + 3 F₂ (g) → 2 TbF₃ (s)  [white]  (Terbium (lll) fluoride)
2 Tb (s) + 3 Cl₂ (g) → 2 TbCl₃ (s)  [white]  (Terbium (lll) chloride)
2 Tb (s) + 3 Br₂ (g) → 2 TbBr₃ (s)  [white]  (Terbium (lll) bromide)
2 Tb (s) + 3 I₂ (g) → 2 TbI₃ (s)                 (Terbium (lll) iodide)
Dissolves readily in dilute sulfuric acid to form Solutions containing Terbium (lll) ions (pale pink):
2 Tb (s) + 3 H₂SO₄(aq) → 2 Tb³⁺(aq) + 3 SO₄²⁻(aq) + 3 H₂↑ (g)

Terbium History

Naming:  From Ytterby (Sweden), Where it was mined
Discovery:  Carl Gustaf Mosander (1843)

Terbium Uses

Terbium is expensive and rare element, so it has few commercial uses.
Some minor uses are in lasers, semiconductor devices, and phosphorous in colour television tubes.

Sodium terbium borate is used in solid-state devices.
 ATerbium can be used with Zirconium dioxide (ZrO₂) as a crystal stabilizer of fuel cells which operate at high temperature.
It is also used in low-energy lightbulbs and mercury lamps.
It has been used to improve the safety of medical x-rays.

Terbium alloyed with dysprosium and iron lengthens and shortens in a magnetic field and has the highest magnetostriction of any alloy useful in magnetomechanical devices (Loudpeakers etc..)
 
Biological role: It is Low-toxic, But it should be handled with care.

Abundance of Terbium  

Found in the minerals monazite and bastnaesite (chiefly in monazite ore).
It can be extracted by ion exchange and solvent extraction.
It is also obtained from euxenite, a complex oxide containing 1% or more of terbiums.

Terbium metal is produced commercially by reducing the anhydrous chloride  or fluoride with calcium metal under a vacuum in a tantalum crucible.
It can also produce by the electrolysis of terbium-oxide in molten calcium chloride.

Annual world wide production is around 10 tons.
5×10^-8% (In Universe)
3.9×10^-6% (In Meteorites)
1×10^-8% (In Sun)
0.000093% (In Earth’s Crust)
1.4×10^-11% (In Oceans)

World’s Top 3 producers of Terbium

1) China
2) Russia
3) Malaysia

World’s Top 3 Reserve holders of Terbium

1) China
2) CIS Countries (inc. Russia)
3) USA

#terbium

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