Difference between revisions of "Terbium"

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[[File:Terbium_by_Brain&Force.jpg|thumb|256px|5.74 grams of distilled terbium metal]]
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{{Infobox element
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|image size=280
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|image name comment=5.74 grams of distilled terbium metal
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<!-- General properties -->
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|name=Terbium
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|symbol=Tb
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|pronounce=
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|pronounce comment=
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|pronounce 2=
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|alt name=
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|allotropes=
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|appearance=Silvery-white
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<!-- Periodic table -->
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|above=
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|below=Bk
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|left=[[Gadolinium]]
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|right=[[Dysprosium]]
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|number=65
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|atomic mass=158.92535(2)
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|atomic mass 2=
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|series=
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|group=
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|period=6
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|period comment=
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|block=f
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|block ref=
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|block comment=
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|electron configuration= [Xe] 4f<sup>9</sup> 6s<sup>2</sup>
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|electron configuration ref=
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|electron configuration comment=
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|electrons per shell=2, 8, 18, 27, 8, 2
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|electrons per shell ref=
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|electrons per shell comment=
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<!-- Physical properties -->
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|physical properties comment=
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|color=Silvery-white
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|phase=Solid
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|phase ref=
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|phase comment=
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|melting point K=1629
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|melting point C=1356
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|melting point F=​2473
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|melting point comment=
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|boiling point K=3396
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|boiling point C=3123
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|boiling point F=5653
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|sublimation point K=
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|density gplstp=
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|density gpcm3nrt=8.23
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|density gpcm3mp=7.65
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|density gpcm3bp=
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|molar volume=
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|triple point K=
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|critical point K=
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|heat fusion=10.15
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|heat vaporization=391
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|heat vaporization ref=
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|heat vaporization comment=
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|heat capacity=28.91
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|heat capacity ref=
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|heat capacity comment=
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|heat capacity 2=
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|heat capacity 2 comment=
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|vapor pressure 1=1789
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|vapor pressure 10=1979
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|vapor pressure 100=(2201)
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|vapor pressure 1 k=(2505)
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|vapor pressure 10 k=(2913)
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|vapor pressure 100 k=(3491)
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<!-- Atomic properties -->
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|atomic properties comment=
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|oxidation states=4, '''3''', 2, 1
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|oxidation states ref=
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|oxidation states comment=(a weakly basic oxide)
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|electronegativity=1.2
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|electronegativity ref=
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|electronegativity comment=
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|ionization energy 1=565.8
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|ionization energy 1 ref=
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|ionization energy 1 comment=
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|ionization energy 2=1110
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|ionization energy 2 ref=
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|ionization energy 2 comment=
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|ionization energy 3=2114
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|ionization energy 3 ref=
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|ionization energy 3 comment=
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|number of ionization energies=
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|ionization energy comment=
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|atomic radius=177
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|atomic radius ref=
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|atomic radius comment=
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|atomic radius calculated=
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|atomic radius calculated ref=
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|atomic radius calculated comment=
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|covalent radius=194±5
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|covalent radius ref=
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|covalent radius comment=
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|Van der Waals radius=
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<!-- Miscellanea -->
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|crystal structure=
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|crystal structure prefix=
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|crystal structure comment=Hexagonal close-packed (hcp)
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|crystal structure 2=
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|speed of sound=
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|speed of sound comment=
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|speed of sound rod at 20=2620
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|speed of sound rod at r.t.=
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|thermal expansion=10.3
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|thermal expansion ref=
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|thermal expansion comment=(α, poly)
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|thermal expansion at 25=
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|thermal expansion at 25 ref=
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|thermal conductivity=11.1
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|electrical resistivity=1.15·10<sup>-6</sup>
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|band gap=
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|Curie point K=
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|magnetic ordering=Paramagnetic
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|magnetic ordering ref=
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|magnetic ordering comment=
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|tensile strength=
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|tensile strength ref=
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|tensile strength comment=
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|Young's modulus=55.7
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|Young's modulus ref=
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|Young's modulus comment=(α form)
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|Shear modulus=22.1
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|Shear modulus ref=
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|Shear modulus comment=(α form)
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|Bulk modulus=38.7
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|Bulk modulus ref=
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|Bulk modulus comment=(α form)
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|Poisson ratio=0.261
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|Poisson ratio ref=
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|Poisson ratio comment=(α form)
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|Mohs hardness=
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|Mohs hardness 2=
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|Mohs hardness 2 comment=
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|Vickers hardness=450–865
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|Vickers hardness ref=
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|Vickers hardness comment=
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|Brinell hardness=675–1200
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|Brinell hardness ref=
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|Brinell hardness comment=
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|CAS number=7440-27-9
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<!-- History -->
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|naming=After Ytterby (Sweden), where it was mined
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|first isolation date=
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|discovery and first isolation by=Carl Gustaf Mosander (1842)
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<!-- Isotopes -->
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|isotopes=
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|engvar=
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}}
 
'''Terbium''' is a [[lanthanide]] with the symbol '''Tb''' and atomic number 65. It is a hard, dark, silvery metal that is about as reactive as [[magnesium]]. Although difficult to find and rather expensive, it and its salts have very interesting properties that make it an excellent addition to the amateur chemist's lab. Among these properties are [[fluorescence]] and [[paramagnetism]], brought about by the element's half-filled f-shell.
 
'''Terbium''' is a [[lanthanide]] with the symbol '''Tb''' and atomic number 65. It is a hard, dark, silvery metal that is about as reactive as [[magnesium]]. Although difficult to find and rather expensive, it and its salts have very interesting properties that make it an excellent addition to the amateur chemist's lab. Among these properties are [[fluorescence]] and [[paramagnetism]], brought about by the element's half-filled f-shell.
  

Revision as of 19:09, 22 October 2017

Terbium,  65Tb
Terbium by Brain&Force.jpg
5.74 grams of distilled terbium metal
General properties
Name, symbol Terbium, Tb
Appearance Silvery-white
Terbium in the periodic table

↑
Tb
↓
Bk
Gadolinium ← Terbium → Dysprosium
Atomic number 65
Standard atomic weight (Ar) 158.92535(2)
Group, block , f-block
Period period 6
Electron configuration [Xe] 4f9 6s2
per shell
 2, 8, 18, 27, 8, 2
Physical properties
Silvery-white
Phase Solid
Melting point 1629 K ​(1356 °C, ​​2473 °F)
Boiling point 3396 K ​(3123 °C, ​5653 °F)
Density near r.t. 8.23 g/cm3
when liquid, at  7.65 g/cm3
Heat of fusion 10.15 kJ/mol
Heat of 391 kJ/mol
Molar heat capacity 28.91 J/(mol·K)
 pressure
Atomic properties
Oxidation states 4, 3, 2, 1 ​(a weakly basic oxide)
Electronegativity Pauling scale: 1.2
energies 1st: 565.8 kJ/mol
2nd: 1110 kJ/mol
3rd: 2114 kJ/mol
Atomic radius empirical: 177 pm
Covalent radius 194±5 pm
Miscellanea
Crystal structure ​Hexagonal close-packed (hcp)
Speed of sound thin rod 2620 m/s (at 20 °C)
Thermal expansion 10.3 µm/(m·K) (α, poly)
Thermal conductivity 11.1 W/(m·K)
Electrical resistivity 1.15·10-6 Ω·m
Magnetic ordering Paramagnetic
Young's modulus 55.7 GPa (α form)
Shear modulus 22.1 GPa (α form)
Bulk modulus 38.7 GPa (α form)
Poisson ratio 0.261 (α form)
Vickers hardness 450–865 MPa
Brinell hardness 675–1200 MPa
CAS Registry Number 7440-27-9
History
Naming After Ytterby (Sweden), where it was mined
Discovery and first isolation Carl Gustaf Mosander (1842)
· references

Terbium is a lanthanide with the symbol Tb and atomic number 65. It is a hard, dark, silvery metal that is about as reactive as magnesium. Although difficult to find and rather expensive, it and its salts have very interesting properties that make it an excellent addition to the amateur chemist's lab. Among these properties are fluorescence and paramagnetism, brought about by the element's half-filled f-shell.

Properties

Physical properties

Terbium is a dark silvery metal that is solid at room temperature. It is quite resistant to impact, but can be scratched with a knife or file.

At room temperature, terbium is paramagnetic and can be picked up easily with a neodymium magnet. This paramagnetism turns to antiferromagnetism at 230 K and to ferromagnetism at 219 K, which is above the temperature of dry ice. This causes a noticeable incrase in magnetic attraction. Terbium has the second-highest Curie temperature of the rare earth elements, exceeded only by gadolinium.

Terbium(III) cations fluoresce to produce bright green light. The fluorescence is generally only visible in the solid state, but certain ligands will allow solutions of these salts to fluoresce in solution. These ions are also paramagnetic, and compounds of terbium(III) may be lifted by a powerful magnet.

Chemical properties

Although terbium is a highly electropositive element, the metal can be stored indefinitely in air and does not corrode, even after years of exposure. However, terbium reacts slowly in cold water, and vigorously in hot water and dilute acids to form trivalent salts.

Terbium reacts with all of the halogens to form trihalides. Small pieces can burn in air with a golden flame to form terbium(III,IV) oxide, which is black, and markedly different from terbium(III) oxide.

In nitric acid, terbium metal will oxidize to both terbium(III) nitrate, which remains in solution, and terbium(III,IV) oxide, which settles to the bottom as a black precipitate.

Terbium sulfate is only poorly soluble in water, and its solubility decreases as temperature increases. Double sulfates with sodium and potassium are even less soluble. Terbium oxalate is extremely insoluble in water.

Terbium(III) is the most stable oxidation state of the element. It is very highly fluorescent. It is not amphoteric, and adding bases such as ammonia to terbium-containing solutions will produce a precipitate of white terbium hydroxide. This hydroxide is itself basic, and will absorb carbon dioxide to form terbium carbonate. This change is not very noticeable.

Terbium(IV) compounds are highly oxidizing. Terbium(III,IV) oxide is a black powder which is similar to manganese dioxide. It can be prepared by igniting terbium(III) oxalate. It is also an excellent catalyst. Terbium(IV) fluoride is one of the best fluorinating agents known, due to its ability to emit relatively pure atomic fluorine, rather than fluoride vapors.

Availability

Terbium is more common than iodine on Earth, but it is very hard to find and expensive. It is also one of the rarest lanthanides, and is in high demand due to its numerous applications. One source for terbium, as well as other rare earth metals, is Metallium. It is sold in 5 gram and 20 gram sizes, as well as rods, ampoules, and coins. Terbium and its compounds occasionally sold on eBay as well.

Projects

Storage and safety

Storage

While there is no problem with storing terbium under an inert argon atmosphere or under mineral oil, terbium does not corrode easily and there is no problem with leaving it in air indefinitely. The pure metal is not affected by the hand moisture when handled without protection.

Toxicity

Toxicity data of terbium compounds is scarce, but they appear to be of low to moderate danger. Terbium plays no biological role, but acts similarly to calcium within the body. Some terbium compounds, notably the halides, will hydrolyze when heated and will give off acidic vapors.

Flammability

Small pieces of terbium metal or terbium powder are flammable. Class D fire extinguishers should be readily available when working with terbium near an open flame. Water should never be used to extinguish burning terbium, as it will aggravate the flame.

References

Relevant Sciencemadness threads

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