Periodic Table > Holmium
 

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 1472 oC, 2681.6 oF, 1745.15 K 
Period Boiling point 2700 oC, 4892 oF, 2973.15 K 
Block Density (kg m-3) 8797 
Atomic number 67  Relative atomic mass 164.93  
State at room temperature Solid  Key isotopes 165Ho 
Electron configuration [Xe] 4f116s2  CAS number 7440-60-0 
ChemSpider ID 22424 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 is based upon the civic coat of arms of Stockholm, the city that gives the element its name.
Appearance
A bright, silvery metal.
Uses
Holmium can absorb neutrons, so it is used in nuclear reactors to keep a chain reaction under control. Its alloys are used in some magnets.
Biological role
Holmium has no known biological role, and is non-toxic.
Natural abundance
Holmium is found as a minor component of the minerals monazite and bastnaesite. It is extracted from those ores that are processed to extract yttrium. It is obtained by ion exchange and solvent extraction.
 
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) 2.300 Covalent radius (Å) 1.79
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
1.230
Ionisation energies
(kJ mol-1)
 
1st
580.986
2nd
1138.526
3rd
2203.723
4th
4100.623
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
  165Ho 164.93 100
 

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)
27.15 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)
- - 3.20
x 10-9
2.32
x 10-5
8.37
x 10-3
0.55 12.3 - - - -
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History

Holmium was discovered at Geneva in 1878 by Marc Delafontaine and Louis Soret, and independently by Per Teodor Cleve at Uppsala, Sweden. Both teams were investigating yttrium, which was contaminated with traces of other rare earths (aka lanthanoids) and had already yielded erbium which was later to yield ytterbium. Cleve looked more closely at what remained after the ytterbium had been removed, and realised it must contain yet other elements because he found that its atomic weight depended on its source. He separated holmium from erbium in 1878. Delafontaine and Soret also extracted it from the same source, having seen unexplained lines in the atomic spectrum. We cannot be certain that either group had produced a pure sample of the new element because yet another rare-earth, dysprosium, was to be extracted from holmium.

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Podcasts

Listen to Holmium Podcast
Transcript :

Chemistry in its element - holmium


(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, mythical monopoles that could lead us into another dimension. 

Hayley Birch 

In 1949, Milton Smith published a short work of fiction that he entitled The Mystery of Element 117. The real element 117 is yet to be discovered - it's a blank space in the Periodic Table just below the halogens. Smith's 117, however, was a strange material that could be used to open a window to another dimension. He called it a magnetic monopole substance - one that instead of having poles, plural, like an ordinary magnet, had a pole. Singular. 

Now, whilst no reputable scientist would argue that a magnetic monopole could open an inter-dimensional portal, its existence isn't outside the realms of possibility and if recent reports are anything to go by, it could depend on an otherwise mundane metallic element that you can find skulking around near the bottom of the Periodic Table - holmium. 

Despite having little else to shout about - bar a silvery sheen and a bit part in controlling nuclear reactions - holmium has some pretty fascinating magnetic properties. In fact, it has the strongest magnetic force of any element, albeit it as a paramagnet, which means it only becomes magnetic when it's sitting in an externally applied magnetic field. 

Perhaps most interesting are recent experiments that involved using holmium to try to find the mythical magnetic monopole. First though, let's create some context. As we know, the monopole has acquired the kind of fringe scientific status that makes it worthy of mention in science fiction circles - besides its appearance in Element 117, the author Larry Niven references monopoles in his 1973 novel Protector, where he imagines one of his characters mining shovelfuls of north poles from the rings of Saturn. 

But monopoles have also been the subject of much real scientific debate. The basis for their existence relies on work by the Nobel Prize-winning physicist Paul Dirac. According to theories, singular magnetic charges - monopoles - must exist in order to adhere to the grand unified theory of physics; to mirror the singular electric charges of elementary particles. 

In 1982, a Stanford University physicist called Blas Cabrera thought he'd found one when, on Valentine's night, his "superconducting quantum interference detector" recorded a massive jump in the current fluctuations it was designed to monitor, indicating the existence of what he claimed to be a monopole. Cabrera and his troop of monopole hunters were given extra funding to build a bigger and better detector, but eventually abandoned their hunt in favour of a search for something similarly mysterious and just as elusive: dark matter. 

Monopoles are even talked about in the same breath as the ever elusive Higg's boson, with whisperings that CERN scientists could create them, along with black holes, in their experiments at the LHC. So last year, when French scientists claimed to have found magnetic components in holmium titanate crystals that behaved for all intents and purposes like monopoles, they sparked a minor media storm. The crystals contained tiny north and south pole points that were separated by less than a nanometre. 

Understandably, however, some scientists took issue with the use of the term "monopole" in this instance and argued that because that because one of these north points couldn't be created without the corresponding south point, the team hadn't found true monopoles. 

So that's about as glamorous and interesting as holmium gets - a minor role in a science fiction story and in a search that may, for all we know, end in nothing but disappointment. And as the 56th most abundant element, it's twenty times more common than silver and hardly deserving of its "rare earth metal" label. In fact, in oxide form, it's used to colour cubic zirconia, the synthetic material that's sold as a cheap substitute for real gemstones. It is also found in very, very small amounts in the body and affects metabolism in certain bacteria, but it doesn't seem to be essential and no one really knows what, exactly, it does. 

But perhaps I've been a bit harsh on poor old holmium, which, to be fair, doesn't get a whole lot of press. Because it does perform another useful task that's deserving of a mention. Some of the most cutting edge lasers used to treat certain cancers are solid-state lasers that require holmium to dope yttrium aluminium crystals. The lasers can be used to vaporise tumours with only minor tissue damage; a patient with early stage bladder cancer can be in and out of hospital in an afternoon without a general anaesthetic. 

So there you have it: mythical monopoles and vaporising lasers. Not bad for an element you barely even knew existed. 

Meera Senthilingam 

So the search for the monopole continues, but vaporising tumours with minimal tissue damage is definitely a noteworthy application of holmium. That was science writer Hayley Birch with the mythical chemistry of holmium. Now, staying on treatments for cancer next week's element also has a radiating way to kill cancer cells. 

Richard Corfield 

225Ac can be used as the active agent Targeted Alpha Therapy, also known as TAT,a technique for inhibiting the growth of secondary cancers by direct irradiation with nuclear material. And so an element discovered in the same mineral - pitchblende - which kick-started the whole science of nuclear chemistry, today stands at the crossroads of one of the most challenging of all medical disciplines - finding a cure for cancer. 

Meera Senthilingam 

And Oxford's Richard Corfield will be revealing more uses for actinium as well as the origin of the actinides 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.