Periodic Table > Thulium
 

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 Lanthanides  Melting point 1545 oC, 2813 oF, 1818.15 K 
Period Boiling point 1950 oC, 3542 oF, 2223.15 K 
Block Density (kg m-3) 9325 
Atomic number 69  Relative atomic mass 168.934  
State at room temperature Solid  Key isotopes 169Tm 
Electron configuration [Xe] 4f136s2  CAS number 7440-30-4 
ChemSpider ID 22400 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 image reflects the origin of the element’s name, and suggests a distant region to the far north (ultima Thule).
Appearance
A bright, silvery metal.
Uses
When irradiated in a nuclear reactor, thulium produces an isotope that emits x-rays. A ‘button’ of this isotope is used to make a lightweight, portable x-ray machine for medical use. Thulium is used in lasers with surgical applications.
Biological role
Thulium has no known biological role. It is non-toxic.
Natural abundance
Thulium is found principally in the mineral monazite, which contains about 20 parts per million. It is extracted by ion exchange and solvent extraction. The metal is obtained by reducing the anhydrous fluoride with calcium, or reducing the oxide with lanthanum.
 
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) 2.270 Covalent radius (Å) 1.77
Electron affinity (kJ mol-1) 99.248 Electronegativity
(Pauling scale)
1.250
Ionisation energies
(kJ mol-1)
 
1st
596.695
2nd
1162.647
3rd
2284.771
4th
4119.920
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 8.0
Country with largest reserve base China
Crustal abundance (ppm) 0.3
Leading producer China
Reserve base distribution (%) 59.30
Production concentration (%) 97.40
Total governance factor(production) 8
Top 3 countries (mined)
  • 1) China
  • 2) USA
  • 3) CIS
Top 3 countries (production)
  • 1) China
  • 2) Russia
  • 3) Brazil
 

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, 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  169Tm 168.934 100
 

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)
27.03 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)
- 6.03
x 10-10
5.94
x 10-5
5.61
x 10-2
5.22 130 - - - - -
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History

Thulium was first isolated in 1879 as its oxide by Per Teodor Cleve at the University of Uppsala, Sweden. The discoveries of the many rare earth elements (aka lanthanoid) began with yttrium in 1794. This was contaminated with these chemically similar elements. Indeed the early chemists were unaware they were there. In 1843, erbium and terbium were extracted from yttrium, and then, in 1874, Cleve looked more closely at erbium and realised that it must contain yet other elements because he observed that its atomic weight varied slightly depending on the source from which it came. He extracted thulium from it in 1879.


In 1911, the American chemist Theodore William Richards performed 15,000 recrystallisations of thulium bromate in order to obtain an absolutley pure sample of the element and so determine exactly its atomic weight.

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Podcasts

Listen to Thulium Podcast
Transcript :

Chemistry in its element - thulium


(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's element takes us into the unknown, entering dark, mysterious lands. 

Brian Clegg 

In medieval times, when maps were bedecked with strange and exotic unknowns, where the corners might be inscribed 'Here be monsters', the most distant place that could be conceived, lying beyond the borders of the known world, was labelled 'Ultima Thule'. Thule is sometimes pronounced Tooli, though it looks as if it should be Thool, which frankly sounds much more suitably dark and mysterious. Originally this was the classical name for a mysterious land, six day's sail to the north of Britain, thought by the Greek historian Polybius to be the most northerly part of the world. 'Ultima Thule' took things one stage further - it was the farthest part of Thule. 

When thulium was named by Per Teodor Cleve in 1879, it was down to a slight misunderstanding of the meaning of thule. Cleve would eventually discover a total of four elements, and won the Davy Medal from the Royal Society for his work on the rare earth metals, but here he wasn't entirely accurate. He wrote 'For the oxide placed between ytterbia and erbia. I propose the name of Thullium derived from Thule, the ancient name of Scandinavia.' Not only had he misplaced Thule, he couldn't even spell it right, putting two L's in the name - but today we spell thulium, like Thule, with a single L. 

Sitting towards the end of the lanthanides, the floating strip of elements on the periodic table that squeezes between barium and lutetium, thulium has atomic number 69. It's one of the rare earths, elements that are largely misnamed as they are quite common. The name reflects the rarity of the original ore in which they were found - but in thulium's case it's not such a bad title as this soft, silvery metal is one of the rarest of the rare earths, and more valuable than platinum. 

The initial discovery of the element was something of an accident. Traces of erbium and terbium had been found when ytrrium was first discovered, though it wasn't initially realized that they were new elements in their own right. Cleve was examining the erbium oxide separated from the mix and found that this too was corrupted. It had a small amount of an unknown substance which gave a slight variation to the atomic weight. The ever finer separation of the contents of this productive ore would eventually yield the oxides of two further elements - hol-mium and finally thulium. 

For a long time thulium was a Cinderella substance. There was nothing you could do with thulium that couldn't be done better and cheaper with one of the other elements. It looked likely that it would be consigned to the dustbin of useless chemical substances. It's notable that one science writer has said of thulium 'the most surprising thing about it is there's nothing surprising about it.' But that's a little unfair. 

Thulium isn't exactly mass market, but about 50 tonnes of it is mined each year, broadly in three bands of ores - Australia and China, the US and Brazil, and India and Sri Lanka. And that's not an effort that would be put in for nothing. 

The only natural isotope of thulium, usually found as an oxide is thulium 169. This is stable, but thulium 170 with a half life of 128 days, produced by bombarding thulium in a nuclear reactor, has proved a good portable source of x-rays. It was first suggested for this role in the 1950s and has frequently turned up since in small scale devices, such as those used in dentist's surgeries. As a low energy source, it's relatively safe, making it a good bet for low tech applications that also find it cropping up in engineering, where the x-rays can be used to hunt for cracks in components. 

Less common, but still valuable, is thulium's role in doping a special type of garnet, yttrium aluminium garnet or YAG. The crystal is used as the active medium in a laser with a wavelength of around 2,000 nanometres, which is ideal for laser surgery, so once again thulium comes to our medical aid. 

Thulium might not have many uses, but it did contribute to the Nobel Prize of American chemist Theodore William Richards. If ever a Nobel Prize was awarded for sheer dogged hard work, then it was the one won by Richards in 1914. The Nobel citation must be one of the least exciting ever made. It was 'in recognition of his accurate determination of the atomic weight of a large number of chemical elements.' But this reflects for thulium alone a total of 15,000 recrystalisation experiments before Richards had a pure enough sample of thulium bromate to be able to fix its atomic weight to his satisfaction (168.93421 to be precise). 

When Per Teodor Cleve named thulium he was working at the University of Uppsala in Sweden, the oldest of the Nordic universities. He wanted to celebrate historic Scandinavian culture - and even if he didn't quite position the mythological land correctly, for Cleve his new discovery would remain the Ultima Thule. 

Meera Senthilingam 

Taking us into distant lands there with the element that comes to our medical aid in lasers and small scale x-rays. That was Science Writer Brian Clegg with the chemistry of Thulium. Now next week, an element that can be manipulated to give us what we want. 

Andrea Sella 

Dark grey in colour and with a very glossy glass-like sheen, it looks like a metal but is in fact quite a poor conductor of electricity, and there in many ways, lies the secret of its ultimate success. By deliberately introducing impurities like boron or phosphorus one can subtly change the electrical behaviour of the element. Such tricks lie at the heart of the functioning of the silicon chips that allow you to listen to this podcast. In less than 50 years silicon has gone from being an intriguing curiosity to being one of the most fundamental elements in our lives. 

Meera Senthilingam 

And to find out more about how crucial Silicon is in our everyday lives, join Andrea Sella in next week's Chemistry in its Element. Until then, I'm Meera Senthilingam and thank you for listening. 

(Promo) 

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

(End promo) 

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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.