Difference between revisions of "Indium"

Revision as of 23:28, 17 January 2018

Indium,  ₄₉In

Disc of indium
General properties
Name, symbol	Indium, In
Appearance	silvery lustrous gray
Indium in the periodic table
Ga ↑ In ↓ Tl Cadmium ← Indium → Tin
Atomic number	49
Standard atomic weight (Ar)	114.818(1)
Group, block	, p-block
Period	period 5
Electron configuration	[Kr] 4d10 5s2 5p1
per shell	2, 8, 18, 18, 3
Physical properties
Silvery-gray
Phase	Solid
Melting point	429.7485 K ​(156.5985 °C, ​313.8773 °F)
Boiling point	2345 K ​(2072 °C, ​3762 °F)
Density near r.t.	7.31 g/cm3
when liquid, at	7.02 g/cm3
Triple point	429.7445 K, ​~1 kPa
Heat of fusion	3.281 kJ/mol
Heat of	231.8 kJ/mol
Molar heat capacity	26.74 J/(mol·K)
pressure
Atomic properties
Oxidation states	3, 2, 1, −1, −2, −5 ​(an amphoteric oxide)
Electronegativity	Pauling scale: 1.78
energies	1st: 558.3 kJ/mol 2nd: 1820.7 kJ/mol 3rd: 2704 kJ/mol
Atomic radius	empirical: 167 pm
Covalent radius	142±5 pm
Van der Waals radius	193 pm
Miscellanea
Crystal structure	​tetragonal
Speed of sound thin rod	1215 m/s (at 20 °C)
Thermal expansion	32.1 µm/(m·K) (at 25 °C)
Thermal conductivity	81.8 W/(m·K)
Thermal diffusivity	83.7 mm2/s (at 300 K)
Magnetic ordering	Diamagnetic
Young's modulus	11 GPa
Mohs hardness	1.2
Brinell hardness	8.8–10.0 MPa
CAS Registry Number	7440-74-6
History
Discovery	Ferdinand Reich and Hieronymous Theodor Richter (1863)
First isolation	Hieronymous Theodor Richter (1867)
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Indium is a chemical element with symbol In and atomic number 49. A post-transition metal, indium is used mostly in electronics, for indium tin oxide transparent conductive coatings.

Properties

Chemical

Indicium is fairly resistant to corrosion and the effects of many chemicals. It does not react with elements such as boron, silicon or carbon when heated together, however it will react with halogens or oxalic acid to give their respective salts.

Indium burns in the presence of oxygen with a blue flame at high temperatures to form indium(III) oxide:

4 In + 3 O₂ → 2 In₂O₃

Indium also forms indium(I) compounds, though they are not as characterized as indium(III) ones. The most well known are indium(I) oxide, which is a black compound and indium(I) sulfide. Both are made at high temperatures and have little applications. Indium(I) halides cyclopentadienyl compounds are also known.

Indium also displays an intermediate oxidation state +2, though only the halides are known and important.

Physical

Indium is a very soft, silvery-grey, highly ductile, relatively rare post-transition metal with a bright luster. Indium is soft enough to be cut with a knife and is soft enough to leave a visible line on paper. Like tin, indium emits a high-pitched "cry" when it is bent. Indium is able to wet glass when melted, property also observed in gallium. Indium has a low melting point, of 156.60 °C and boils at 2072 °C. Its density at room temperature is 7.31 g/cm³.

Availability

Indium is sold by various chemical suppliers, though it's expensive. GalliumSource sells 1 kg of indium at $ 840, while 10 g are available at $ 20.

Certain solders contain small amounts of indium.

Isolation

Indium can be extracted from solders or transparent coatings by dissolving them in acid and then obtained from its salts via either reduction with zinc metal or electrowinning.

Projects

• Demonstration of metal "cry"
• Low melting point alloys

Handling

Safety

Indium does not have any metabolic role in any organism. Due to its position in group 13, its chemical properties are similar to that of aluminium compounds. Indium(III) ions have shown to have a toxic effect on the kidneys when given by injection, however, when taken orally, indium compounds do not have the chronic toxicity of salts of heavy metals, due to poor absorption in basic conditions.

Storage

Indium should be stored in closed containers. As it tends to wet glass, it's best to keep it in plastic containers.

Disposal

Due to its high price, it's best to try to recycle indium, rather than just throw it away.

References

Relevant Sciencemadness threads

• Pure In from 50/50 In/Pb
• Indium compounds