Periodic Table > Indium
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses and properties facts below.

 

Fact box terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact box

 
Group 13  Melting point 156.6 oC, 313.88 oF, 429.75 K 
Period Boiling point 2072 oC, 3761.6 oF, 2345.15 K 
Block Density (kg m-3) 7290 
Atomic number 49  Relative atomic mass 114.818  
State at room temperature Solid  Key isotopes 115In 
Electron configuration [Kr] 4d105s25p1  CAS number 7440-74-6 
ChemSpider ID 4514408 ChemSpider is a free chemical structure database
 

Uses and properties terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses and properties

 
Image explanation
The symbol used here is the Japanese kanji character ‘hon’. It means ‘origin’. Indium is named after the bright indigo line in its spectrum. The Japanese discovered that cotton was a difficult fabric to dye, except with indigo. So, indigo dye was widely used to colour cotton throughout the Edo period (1603–1867).
Appearance
A soft, silvery metal that is stable in air and water.
Uses
Most indium is used to make indium tin oxide (ITO), which is an important part of solar panels and flatscreen TVs. This is because it conducts electricity, bonds strongly to glass and is transparent.

Indium nitride, phosphide and antimonide are semiconductors used in transistors and microchips.

Indium metal sticks to glass and can be used to give a mirror finish to windows of tall buildings, and as a protective film on welders’ goggles. It has also been used to coat ball bearings in Formula 1 racing cars because of its low friction.

An indium alloy has been used for fire-sprinkler systems in shops and warehouses because of its low melting point.
Biological role
Indium has no known biological role. It is toxic if more than a few milligrams are consumed and can affect the development of an embryo or foetus.
Natural abundance
Indium is one of the least abundant minerals on Earth. It has been found uncombined in nature, but typically it is found associated with zinc minerals and iron, lead and copper ores. It is commercially produced as a by-product of zinc refining.
 
Atomic data terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic data

 
Atomic radius, non-bonded (Å) 1.930 Covalent radius (Å) 1.42
Electron affinity (kJ mol-1) 28.935 Electronegativity
(Pauling scale)
1.780
Ionisation energies
(kJ mol-1)
 
1st
558.298
2nd
1820.706
3rd
2704.482
4th
5210.204
5th
-
6th
-
7th
-
8th
-
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Scarcity factor 6.5
Country with largest reserve base n/a
Crustal abundance (ppm) 0.052
Leading producer China
Reserve base distribution (%) n/a
Production concentration (%) 51.30
Total governance factor(production) 6
Top 3 countries (mined)
  • 1) n/a
Top 3 countries (production)
  • 1) China
  • 2) S. Korea
  • 3) Japan
 

Oxidation states and isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation states and isotopes

 
Common oxidation states 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  115In 114.904 95.71 4.4 x 1014 β- 
 

Pressure and temperature - advanced terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure and temperature data – advanced

 
Molar heat capacity
(J mol-1 K-1)
26.74 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- 8.31
x 10-11
1.08
x 10-5
1.27
x 10-2
1.41 40.9 - - - - -
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History

Indium was discovered in 1863 by Ferdinand Reich at the Freiberg School of Mines in Germany. Reich was investigating a sample of the mineral zinc blende (now known as sphalerite, ZnS) which he believed might contain the recently discovered element thallium. From it he obtained a yellow precipitate which he thought was thallium sulfide, but his atomic spectroscope showed lines that were not those of thallium. However, because he was colour-blind he asked Hieronymous Richter to look at the spectrum, and he noted a brilliant violet line, and this eventually gave rise to the name indium, from the Latin word indicum meaning violet.


Working together Reich and Richter isolated a small sample of the new element and announced its discovery. Subsequently the two men fell out when Reich learned that when Richter, on a visit to Paris, claimed he was the discover.

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Podcasts

Listen to Indium Podcast
Transcript :

Chemistry in its element - Indium


(Promo) 

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.

(End promo) 


Meera Senthilingam 

This week, the rare, lustrous element that we have to thank for our flat screen TVs and computer monitors. To tell us more about the chemistry of indium here's Claire Carmalt. 


Claire Carmalt

Until 1924 a gram or so constituted the world's supply of indium in its isolated form. Today around 480 tonnes are produced annually from mining and a further 650 tonnes annually from recycling. So why all the need for indium and what are the unique properties of it that makes it a much sought after element? 


Indium is relatively rare with its abundance in the Earth's crust estimated to be around 0.1 parts per million. Hence it is slightly more abundant than silver or mercury. Indium is generally found in ores of zinc and is produced mainly from residues generated during zinc ore processing. Indium is a moderately toxic metal by inhalation and mildly toxic by ingestion. However, the exact nature of its human toxicity is not clearly understood. 


Indium is a soft, malleable metal with a brilliant lustre. The name indium originates from the indigo blue it shows in a spectroscope. Indium has a low melting point for metals and above its melting point it ignites burning with a violet flame. Bizarrely, the pure metal of indium is described as giving a high-pitched "cry" when bent. This is similar to the sound made by tin or the 'tin cry", however, neither of them is really much like a cry! 


It has the unusual property of remaining soft and workable at very low temperatures. This property allows it to be used in special equipment needed for temperatures near absolute zero. It is an excellent choice for cryogenic pumps, high vacuum systems and other unique joining and sealing applications. Indium lends itself to this application due to its ability to conform to many irregular surfaces and its characteristic "stickiness". Indeed, when pure, it sticks very tightly to itself or to other metals. This property makes it useful as a solder - it reduces the melting point of some solders, strengthens others, and prevents some solders from breaking down too easily. For example, when used as a washer between a silicon diode or other temperature sensors and refrigerator cold stages, indium foil increases the thermal contact area and prevents the sensor from detaching due to vibration. Other uses of indium are in the manufacture of batteries and electronic devices, and in research. 


Another important use of indium is in making alloys - used in electronic devices and dental materials. Indium has been called a "metal vitamin" in alloys, which means that very small amounts of indium can make big changes in an alloy. For instance, the addition of small amounts of indium to gold and platinum alloys makes them much harder. Some aircraft parts are made of alloys that contain indium and it prevents them from reacting with oxygen in the air or wearing out. 


Indium metal dissolves in acids, but does not react with oxygen at room temperature. However, at higher temperatures, it combines with oxygen to form indium oxide. It is in this form that indium finds application as a transparent conductive oxide. As the name indicates these materials, when applied as a thin coating onto glass or plastic films, are both transparent to visible light as well as electrically conductive. It is actually Indium Tin Oxide or "ITO" which is used and this is one of the most important applications of indium. 


About 45% of all indium is used to make ITO and this finds application in solar cells and flat panel displays (LCDs - liquid crystal displays). For both of these applications the ITO is used to establish an electric current over the device and to pass light through it. When architectural or photovoltaic glass is coated with ITO it keeps the harmful infrared rays of the sun from passing through. If coated onto aircraft or automotive windshields, it allows the glass to be electrically deiced or demisted as well as reducing the air conditioning requirement by reducing heat gain. Other compounds of indium used in solar cells include indium gallium arsenide and copper indium gallium selenide. Many scientists think that solar cells may replace natural gas, coal and oil for many applications in the future. However, the availability of indium has been questioned since the demand has risen rapidly in recent years with the popularity of LCD televisions and computer monitors. On the free indium market, this has lead to considerable price increases and the unavailability of sizeable quantities of indium. Currently, increased recycling and manufacturing efficiency maintain a good balance between demand and supply. 


Meera Senthilingam 

So, an element with a multitude of uses, varying from solar cells and windscreen demisters to LCD screens, batteries and even dental materials. No wonder we need to recycle it to meet the element's demand. That was University College London's Claire Carmalt with the chemistry and uses of indium. Now next week an element that changed the rules of nature. 


Eric Scerri 

Until the early 1960s it was believed that three bonds between any two atoms was as high as Nature could go, as in the case of the nitrogen-nitrogen triple bond for example. But in 1964 Albert Cotton and co-workers in the USA discovered the existence of a metal-metal quadruple bond. Yes you guessed it, it as rhenium! 


Meera Senthilingam 

Join UCLA's Eric Scerri to find out what other surprises rhenium has in store in next weeks Chemistry in its Element. Until then I'm Meera Senthilingam from the Naked Scientists.com and thank for listening. 


(Promo) 

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements

(End promo) 

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Description :
This experiment illustrates the displacement of copper from copper(II) sulfate solution using aluminium foil.
Description :
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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.