Periodic Table > Gadolinium
 

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 1313 oC, 2395.4 oF, 1586.15 K 
Period Boiling point 3273 oC, 5923.4 oF, 3546.15 K 
Block Density (kg m-3) 7870 
Atomic number 64  Relative atomic mass 157.25  
State at room temperature Solid  Key isotopes 158Gd 
Electron configuration [Xe] 4f75d16s2  CAS number 7440-54-2 
ChemSpider ID 22418 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 past use of the element in television screens.
Appearance
A soft, silvery metal that reacts with oxygen and water.
Uses
Gadolinium has useful properties in alloys. As little as 1% gadolinium can improve the workability of iron and chromium alloys, and their resistance to high temperatures and oxidation. It is also used in alloys for making magnets, electronic components and data storage disks.

Its compounds are useful in magnetic resonance imaging (MRI), particularly in diagnosing cancerous tumours.

Gadolinium is excellent at absorbing neutrons, and so is used in the core of nuclear reactors.
Biological role
Gadolinium has no known biological role, and has low toxicity.
Natural abundance
In common with other lanthanides, gadolinium is mainly found in the minerals monazite and bastnaesite. It can be commercially prepared from these minerals by ion exchange and solvent extraction. It is also prepared by reducing anhydrous gadolinium fluoride with calcium metal.
 
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) 2.340 Covalent radius (Å) 1.82
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
1.200
Ionisation energies
(kJ mol-1)
 
1st
593.365
2nd
1166.507
3rd
1990.491
4th
4245.351
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
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  152Gd 151.92 0.2
  154Gd 153.921 2.18
  155Gd 154.923 14.8
  156Gd 155.922 20.47
  157Gd 156.924 15.65
  158Gd 157.924 24.84
  160Gd 159.927 21.86 > 1.9 x 1019 β-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)
37.03 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)
- - - 5.70
x 10-10
1.54
x 10-6
4.29
x 10-4
2.79
x 10-2
0.62 7.39 56.2 -
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History

Gadolinium was discovered in 1880 by Charles Galissard de Marignac at Geneva. He had long suspected that the didymium reported by Carl Mosander was not a new element but a mixture. His suspicions were confirmed when Marc Delafontaine and Paul-Emile Lecoq de Boisbaudran at Paris reported that its spectral lines varied according to the source from which it came. Indeed, in 1879 they had already separated samarium from some didymium which had been extracted from the mineral samarskite, found in the Urals. In 1880, Marignac extracted yet another new rare earth from didymium, as did Paul-Émile Lecoq de Boisbaudran in 1886, and it was the latter who called it gadolinium.

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Podcasts

Listen to Gadolinium Podcast
Transcript :

Chemistry in Its Element - Gadolinium


(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 Senthilingham

This week: the art of naming an element. Here's Simon Cotton:

 

Simon Cotton

It's always interesting to know where an element takes its name. The family of elements that we call the lanthanides, or lanthanoids, have a somewhat random selection of names. That's because identifying the 15 lanthanide elements took over one hundred and fifty years, from the isolation of the first compounds to the synthesis of the last lanthanide, radioactive promethium, in 1947. 

Some are named after gods, such as cerium; some like europium are named after places; and others including gadolinium, the star of this podcast, derive their names from scientists.

Gadolinium is named after Johan Gadolin, a Finnish scientist who was both a chemist and geologist. In 1792 he isolated the first rare earth compound, what we now know as yttrium oxide, from a black mineral that had been discovered at Ytterby in Sweden. A few years later this ore, which contained a number of lanthanides, was named gadolinite. Because of the difficulty in separating the very similar lanthanides, it was not until 1880 that a Swiss chemist named de Marignac identified spectroscopic lines due to the element we now know as gadolinium. Six years later, in 1886, the French chemist de Boisbaudran isolated the pure oxide, and called the element gadolinium, as it was obtained from gadolinite. Metallic gadolinium was not isolated until 1935, and like all the other lanthanides, it is a reactive metal.

Nearly all the known chemistry of gadolinium is that of the gadolinium three plus (3+) ion. This ion is colourless and does not at first glance seem very interesting. But like most other lanthanides and indeed transition metals, it has several unpaired electrons, giving it interesting magnetic properties. In fact this ion has 7 unpaired electrons in its 4f orbitals giving it a very large magnetic moment, and scientists are currently interested in making use of this.

As everyone knows, chlorofluorocarbons, CFCs for short, have been widely used in the past in fridges and freezers as the refrigerant gas. CFCs contribute to both depleting the Ozone layer and they are also Greenhouse gases, and due to this their use in the developed world has largely ceased. Meaning a good, more environmentally friendly, replacement is needed. Gadolinium may prove useful the fridges of the future due to a process known as magnetic refrigeration or adiabatic demagnetisation.

It works like this: - 
When a substance containing unpaired electrons is put into a magnetic field, the magnetic dipoles tend to align with the field, in the lowest energy state; this process releases heat, which can be taken away using an external cooling liquid. Now if you remove the coolant from the magnetic material, and switch off the magnetic field. The magnetic dipoles in the material randomises, and it cools down.

A magnetic fridge has actually been constructed making use of gadolinium's ability to do this. The fridge contains a wheel with segments of powdered gadolinium, and as the wheel turns it passes through a gap between the poles of a very powerful magnet. When gadolinium is in the magnetic field it heats up, so it has to be cooled down by passing water through it. 

Then as the wheel turns and the gadolinium leaves the magnetic field, the gadolinium starts to cools even more. A second lot of water is then flowed over the metal, which in turn is cooled down. This cool water is then circulated through the cooling coils of the fridge. 

It's makers based at Iowa State University, say that this 'magnetic' refrigeration is 20 to 30 percent more energy efficient than conventional refrigeration - adding to its 'green' credentials.

That use may lie in the future, but the use of gadolinium in Magnetic Resonance Imaging is very much in the present.

MRI is a routine non-invasive clinical method used to produce two-dimensional images of our tissues or organs for diagnostic purposes. When searching for blood vessels or tumours, contrast agents are injected intravenously to improve the image quality of the MRI signal, and these are normally aqueous solutions of gadolinium complexes. 

The free Gd3+ ion has a similar ionic radius to Ca2+ but a greater charge, so gadolinium itself can not be used as it might interfere with various calcium roles in signalling within the body and therefore be toxic. So the gadolinium ions are turned into stable complexes before being used, by reacting them with ligands like diethylenetriamine pentacetic acid, known as DPTA. This ligand has 8 atoms to attach to gadolinium, meaning it is bound very tightly indeed, ensuring free, toxic, gadolinium is not released. Once injected the compound circulates though the vascular system and then is filtered out through the kidneys and excreted unchanged. All the evidence suggests that it is quite safe, but at present its use in pregnant women is discouraged, largely because its safety for the foetus has not been proved. 

So Gadolinium - colourless and initially may not sound very interesting, but may hold the key to keeping your milk or butter cool without damaging our environment and may even help save your life.

 

Meera Senthilingham

So offering the potential to save our lives and the environment - quite an element. That was Uppingham School's Simon Cotton with the heroic chemistry of gadolinium. Now, next week, we go back to the importance of naming an element, but also its pronunciation.

 

Brian Clegg

You'd think it is pretty strightforward to decide what an element is called, but element 102 has had more than its fair share of misunderstandings and arguments. To begin with, there's the matter of how to pronounce its current name: no-bell-ium, as it comes from the same root as the Nobel prize; or no-beel-ium, modelled on the way we say 'helium'. Even the Royal Society of Chemistry's representatives had a raging discussion on this when I asked them, before plumping for no-beel-ium. And that's just the pronunciation, the name itself took a fair amount of sorting out.

 

Meera Senthilingham

And join Brian Clegg to find out how element 102 received its name, as well as the wonders of its chemistry, in next week's Chemistry in its element. Until then, thank you for listening, I'm Meera Senthilingham.

 

(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.