Periodic Table > Promethium
 

Terminology


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


For more information on Murray Robertson’s image see Uses/Interesting 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 1042 oC, 1907.6 oF, 1315.15 K 
Period Boiling point 3000 oC, 5432 oF, 3273.15 K 
Block Density (kg m-3) 7220 
Atomic number 61  Relative atomic mass 144.913  
State at room temperature Solid  Key isotopes 145Pm, 147Pm 
Electron configuration [Xe] 4f56s2  CAS number 7440-12-2 
ChemSpider ID 22386 ChemSpider is a free chemical structure database
 

Interesting Facts 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 / Interesting Facts

 
Image explanation
The imagery used is based on a scene from an Ancient Greek vase which depicts the god Atlas witnessing Zeus' punishment of Prometheus which was to be chained to a rock on a mountain peak. Every day an eagle tore at Prometheus's body and ate his liver, and every night the liver grew back. Because Prometheus was immortal, he could not die. But he suffered endlessly.
Appearance
A radioactive element whose longest lived isotope, promethium-145, has a half-life of only 18 years. It is obtained in milligramme amounts from nuclear reactors, and a little is used in specialised miniature batteries.
Uses
Promethium is used in batteries as it can capture light in photocells and convert it into an electric current. Such batteries are used in watches, radios and guided-missile instruments. They are no larger than a drawing pin.
Biological role
Promethium has no known biological role, but is toxic due to its radioactivity.
Natural abundance
Promethium is not found on the planet Earth. It has been identified in the galaxy of Andromeda. It can be produced by the irradiation of neodymium and praseodymium with neutrons, deuterons and alpha particles. It can also be prepared by ion exchange of atomic reactor fuel processing wastes.
 
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) 2.380 Covalent radius (Å) 1.86
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
Unknown
Ionisation energies
(kJ mol-1)
 
1st
538.581
2nd
1051.689
3rd
2151.621
4th
3965.544
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/ 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 / Isotopes

 
Common oxidation states 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  145Pm 144.913 - 17.7 y  EC 
  147Pm 146.915 - 2.623 y  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 / Temperature - 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

In 1902, Bohuslav Branner speculated that there should be an element in the periodic table between neodymium and samarium. He was not to know that all its isotopes were radioactive and had long disappeared. Attempts were made to discover it and several claims were made, but clearly all were false. However, minute amounts of promethium do occur in uranium ores as a result of nuclear fission, but in amounts of less than a microgram per million tonnes of ore.


In 1939, the 60-inch cyclotron at the University of California was used to make promethium, but it was not proven. Finally element 61 was produced in 1945 by Jacob .A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell at Oak Ridge, Tennessee. They used ion-exchange chromatography to separate it from the fission products of uranium fuel taken from a nuclear reactor.

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Podcasts

Listen to Promethium Podcast
Transcript :

Chemistry in its element - promethium


(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, we enter the world of Greek mythology to reveal the great powers of the element promethium. 

Brian Clegg 

Of all the figures in Greek myth, Prometheus has to be one of the most significant for science. This Titan brought fire to mankind. For that gift he was punished by having his liver pecked out by an eagle every day. Such was the reward for being an early technologist. 

In other legends Prometheus gave us maths and science, agriculture and medicine - or even created humans in the first place. This uncertainty of just what Prometheus was responsible for is echoed in the uncertainty of who discovered the element promethium, number 61 in the periodic table. 

We know who named it. That was Grace Coryell, the wife of Charles Coryell who with colleagues Jacob Marinsky and Lawrence Glendenin produced promethium at the Oak Ridge National Laboratory, near Knoxville, Tennessee, in 1945. Mrs Coryell allegedly felt they were, like Prometheus, stealing fire from the gods - presumably a reference to the atomic bomb programme, rather than anything significant about promethium itself. But this wasn't the first reference to element 61. 

As far back as 1902 there were suspicions that such an element should exist. Promethium sits in the lanthanides, the floating bar of elements that squeezes between barium and lutetium. The rare earth elements either side of it, neodymium and samarium, seemed not to have the right relationship in their chemical properties to be neighbours. It was as if there were a gap between, and Czech chemist John Bohuslav Branner suspected that a missing element occupied that gap. 

This suspicion was reinforced by Henry Moseley, the English physicist who gave structure to the concept of atomic number, realizing that it reflected the number of protons in an atom's nucleus. What had, until then, been a rather arbitrary numbering system was given a specific meaning - and in 1914, Moseley realized that there was a missing element in number 61. 

Before Coryell's team isolated promethium there were at least two others in the 1920s who claimed to have found element 61. An Italian team found something they named florentium after their city, while an American group in Illinois came up with illinium. Both these findings were announced in 1926, with the Americans publishing first, promptly followed by the Italians, who claimed priority because they had results locked away in a safe dating back two years. But in practice neither of these findings could be duplicated, and apart from a failed 1938 attempt at Ohio State University, the discovery remained unclaimed until the 1945 isolation of promethium. It was a by-product of uranium fuel in one of the early reactors being used to produce plutonium for the atomic bomb. Coryell's team intended to call it clintonium, after the Clinton Laboratories where they worked, until Mrs Coryell persuaded them that the classical name was better. 

One of the reasons promethium was so elusive for a relatively low atomic number element is that it doesn't have a stable state - it's one of only two elements below 83 that only has radioactive isotopes, the other being technetium. The most stable form of promethium has a half life of just 17.7 years - that's promethium 145 - so it's hardly surprising that it proved difficult to pin down, though it does occur naturally in tiny quantities in the ore pitchblende when uranium 238 splits spontaneously. The amounts produced are so small - around a trillionth of a gram from a tonne of ore - that promethium was unlikely to be discovered this way. However it would be wrong to say that promethium is negligible in nature. It has been detected using spectroscopes, devices that analyze materials from the light they give off, on the star HR465 in the constellation Andromeda. No one is quite sure why this star is pumping out what must be considerable quantities of promethium. 

This grey metallic element gives off beta particles - electrons from the nucleus - as it decays. These can cause radioactive damage in their own right, but prometheum is probably most dangerous because those beta particles generate X-rays when they hit heavy nuclei, making a sample of promethium bathe its surroundings in a constant low dosage X-ray beam. 

It was initially used to replace radium in luminous dials when it was realized that radium was too dangerous. Promethium chloride was mixed with phosphors that glow yellowy-green or blue when radiation hits them. However, as the dangers of the element's radioactive properties became apparent, this too was dropped from the domestic glow-in-the-dark market, only used now in specialist applications. 

The obvious use of promethium is for portable X-ray devices, though this isn't an application that has been properly developed yet. Instead the element's beta radiation has been used in industry to measure the thickness of materials, and the isotope promethium 147 has been used in nuclear batteries. These are long life power sources that make use of the beta radiation (which is, after all, made up of electrons, the source of an electrical current) to generate power. Such batteries, often less than a centimetre across, can keep in action for around five years, twice promethium 147's half life. They have been used in everything from missiles to pacemakers. 

In its early days, nuclear power seemed to promise vast amounts of cheap, portable energy. Science fiction of the period featured walnut-sized generators that could run a household, all driven by nuclear fission. In nuclear batteries, promethium comes about as close as we've ever got to a portable nuclear powered energy source. So in that small way at least, it lives up to the titan it was named after - Prometheus, the bringer of fire. 

Meera Senthilingam 

So a provider of portable and long life power named after the bringer of fire. That was science writer Brian Clegg bringing us the powerful and mythological chemistry of Promethium. Now next week an element that shoots us off into outer space, quite literally. 

Richard Corfield 

Despite its rarity and hazards it seems appropriate that an element first synthesised during a global conflict that saw the development of the vehicles that would one day take us to the Moon and beyond is now so pivotal to space exploration, providing our robotic pioneers not only with power but also the ability to analyse extraterrestrial materials as well. 

Meera Senthilingam 

Trying to guess what wondrous element this is? Join Richard Corfield to find out the discovery, chemistry and applications of the element Curium 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.