Periodic Table > Fermium
 

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 Actinides  Melting point 1527 oC, 2780.6 oF, 1800.15 K 
Period Boiling point Unknown 
Block Density (kg m-3) Unknown 
Atomic number 100  Relative atomic mass 257.095  
State at room temperature Solid  Key isotopes 257Fm 
Electron configuration [Rn] 5f127s2  CAS number 7440-72-4 
ChemSpider ID 22434 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 aims to suggest a self-propagating nuclear chain reaction, such as occurs in nuclear reactors and atomic bombs.
Appearance
A radioactive metal obtained only in microgram quantities.
Uses
Fermium has no uses outside research.
Biological role
Fermium has no known biological role. It is toxic due to its radioactivity.
Natural abundance
Fermium can be obtained, in microgram quantities, from the neutron bombardment of plutonium in a nuclear reactor.
 
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) 2.450 Covalent radius (Å) 1.67
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
Unknown
Ionisation energies
(kJ mol-1)
 
1st
627.154
2nd
-
3rd
-
4th
-
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 Unknown
Country with largest reserve base Unknown
Crustal abundance (ppm) Unknown
Leading producer Unknown
Reserve base distribution (%) Unknown
Production concentration (%) Unknown
Total governance factor(production) Unknown
Top 3 countries (mined)
  • Unknown
Top 3 countries (production)
  • Unknown
 

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
  257Fm 257.095 - 100.5 d  α 
        sf 
 

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)
Unknown 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)
- - - - - - - - - - -
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History

Fermium was discovered in 1953 in the debris of the first thermonuclear explosion which took place on a Pacific atoll on 1 November 1952. In this a uranium-238 bomb was used to provide the heat necessary to trigger a thermonuclear explosion. The uranium-238 had been exposed to such a flux of neutrons that some of its atoms had captured several of them, thereby forming elements of atomic numbers 93 to 100, and among the last of these was an isotope of element 100, fermium-255. News of its discovery was kept secret until 1955.


Meanwhile a group at the Nobel Institute in Stockholm had independently made a few atoms of fermium by bombarding uranium-238 with oxygen nuclei and obtained fermium-250, which has a half-life of 30 minutes.

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Podcasts

Listen to Fermium Podcast
Transcript :

Chemistry in Its Element - Fermium


(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, all rise for element 100. Here's Brian Clegg

 

Brian Clegg

The number 100 is a very significant one for human beings. It's partly because our number system is based on ten - so ten tens seems to have a special significance. In years, it's around the maximum lifetime of a human being, making a century more than just a useful division in the historical timeline. But in the natural world, 100 isn't quite so important. There's nothing about being element 100 that makes fermium stand out - the periodic table doesn't attach any significance to base 10. But it's hard not to think that fermium must be special in some way.

Like element 99 (einsteinium), fermium was first made in the hydrogen bomb test on Elugelab Island on the Eniwetok Atoll in the South Pacific. The test bomb exploded on the first of November 1952*, blasting vast quantities of material into the atmosphere that drifted down as fallout. The team from the University of Berkeley at California that tested tonnes of ash and coral debris found around 200 atoms of element 100.

This had been created from uranium 238. Fusion in the hydrogen bomb was triggered by a conventional atomic bomb, and the remnants of that trigger's uranium fuel absorbed a swathe of neutrons, some of which then changed to protons as they underwent beta decay, finally producing fermium 255.

The discoverers aptly named the element after Enrico Fermi, the Italian-born physicist whose work at the University of Chicago was crucial to the development of nuclear explosives. This work took place under the bleachers of a dusty, disused football stadium. The site hadn't been used for three years since the president of Chicago University closed down the football team as a distraction from academic work. In a claustrophobic space beneath the stands was an old squash court. Here, in 1942, Fermi and his team built the world's first manmade nuclear reactor, literally an atomic pile of carbon bricks where materials for the atomic bomb would be produced. Fermi, who won the Nobel Prize in 1938, also worked in quantum mechanics and particle physics, making him an ideal candidate for an elementary name.

The element was almost named centurium, however. In 1953, scientists at the Nobel Institute in Stockholm had produced fermium 250 by bombarding uranium with oxygen nuclei. At the time, the discoveries from the hydrogen bomb were classified, so the Swedes, who tentatively came up with the centurium name for one hundred, could have got in first, had fermium not been rapidly de-classified. It might be no coincidence that the Berkeley team allowed the Nobel Institute's name nobelium for element 102 to continue to be used when the Swedes' claim for discovering that element proved dubious. There could have been a certain amount of guilt for sneaking in fermium under their noses.

Fermium is an actinide, part of the floating bar of elements that is squeezed out from between actinium and lawrencium. Perhaps its greatest claim to fame on the periodic table is that it defines the start of the most obscure of the artificial elements - those above 100 are referred to as the transfermium elements. It is certainly the highest numbered element that has had a practical use identified. 

Although not yet deployed, fermium 255 is a strong alpha particle emitter with a half life - the time it takes half the material to undergo nuclear decay - of around 20 hours. In medical radioactive applications this is a good combination, where alpha sources are used in radiotherapy for cancer. This is a convenient half-life as it means the alpha particles - nuclei of helium atoms with two protons and two neutrons - are produced long enough for the source to be deployed, but the waste matter becomes a low level hazard very quickly.

Fermium is usually produced using accelerators like cyclotrons now, although it has a special place in the periodic table as the highest numbered element that can be produced in a nuclear reactor, rather than by smashing atoms together in an accelerator. This is something of a useless capability, however. The fermium produced in reactors seems a good, useable product. It's fermium 257, which has a very practical half life of 100 days. But there's never a chance to use it. Inside a reactor there are plenty of loose neutrons floating about - this is how the chain reaction of the reactor works. Fermium 257 is great at absorbing neutrons and immediately become fermium 258. This has a tiny half life of less than a millisecond. So before you can get your hands on the fermium produced in a reactor it has disappeared.

Like its transfermium colleagues, fermium has only been made in relatively tiny quantities. This means that no one has produced a big enough sample of fermium to be able to see it, though the expectation is that like other similar elements it would be a silvery-grey metal.

Fermium has limited value, but anything numbered 100 inevitably feels a little special. And perhaps fermium is, at least when it's made in a nuclear reactor. You can see fermium as a sneaky element. As we've seen, this is a product that you can make, that should last 100 days before half of it has disappeared, yet in practice it vanishes after milliseconds. Perhaps what makes fermium special is that it's an element with a wicked sense of humour.

Meera Senthilingham

So the element that scientists are trying - and failing - to get their hands on. That was Brian Clegg, with the disappearing properties of fermium. Now next week, and element that we can see, and it's a lanthanide with a diverse range of applications.

Simon Cotton

Lutetium and its compounds have found some applications, the most important of these is the use of the oxide in making catalysts for cracking hydrocarbons in the petrochemical industry. But there are other more specialist uses, such as using the radioactive Lutetium-177 isotope in cancer therapy. Lutetium ions were also used to dope gadolinium gallium garnet to make magnetic bubble computer memory that was eventually replaced by modern-day hard drives. 

Lutetium triflate has also been found to be a very effective recyclable catalyst for organic synthesis in aqueous systems - it avoids the use of organic solvents giving it green credentials.

Meera Senthilingham

And to find out the chemistry and properties of lutetium that make it so widely applicable, join Simon Cotton in next week's Chemistry in its element. until then, I'm Meera Senthilingham 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)

 

*The correct date is 1952, not 1942 as in the podcast audio file

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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.