Periodic Table > Curium
 

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 (g cm-3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.


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 1345 oC, 2453 oF, 1618 K 
Period Boiling point Unknown 
Block Density (g cm-3) 13.51 
Atomic number 96  Relative atomic mass [247]  
State at 20°C Solid  Key isotopes 243Cm, 248Cm 
Electron configuration [Rn] 5f76d17s2  CAS number 7440-51-9 
ChemSpider ID 22415 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 shows a satellite in orbit around the Earth, reflecting the use of curium in satellite technology.
Appearance
A radioactive metal that is silver in colour. It tarnishes rapidly in air.
Uses
Curium has been used to provide power to electrical equipment used on space missions.
Biological role
Curium has no known biological role. It is toxic due to its radioactivity.
Natural abundance
Curium can be made in very small amounts by the neutron bombardment of plutonium in a nuclear reactor. Minute amounts may exist in natural deposits of uranium. Only a few grams are produced each year.
 
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) 2.45 Covalent radius (Å) 1.68
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
Unknown
Ionisation energies
(kJ mol-1)
 
1st
578.082
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 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 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.


Political stability of top producer

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 distribution (%), Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply risk

 
Relative supply risk Unknown
Crustal abundance (ppm) Unknown
Recycling rate (%) Unknown
Substitutability Unknown
Production concentration (%) Unknown
Reserve distribution (%) Unknown
Top 3 producers
  • Unknown
Top 3 reserve holders
  • Unknown
Political stability of top producer Unknown
Political stability of top reserve holder 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 4, 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  243Cm 243.061 - 29.1 y  α 
        5.5 x 1011 sf 
  244Cm 244.063 - 18.1 y  α 
        1.32 x 107 sf 
  245Cm 245.065 - 8.48 x 103 α 
        1.4 x 1012 sf 
  246Cm 246.067 - 4.76 x 103 α 
        1.8 x 107 sf 
  247Cm 247.070 - 1.56 x 107 α 
  248Cm 248.072 - 3.48 x 105 α 
 

Pressure and temperature - advanced terminology


Specific heat capacity (J kg-1 K-1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram 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

 
Specific heat capacity
(J kg-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)
- - - 1.90
x 10-9
4.24
x 10-6
0.00103 0.0629 1.17 12.1 82.1 -
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History

Curium was first made by the team of Glenn Seaborg, Ralph James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley, California. They bombarded a piece of the newly discovered element plutonium (isotope 239) with alpha-particles. This was then sent to the Metallurgical Laboratory at the University of Chicago where a tiny sample of curium was eventually separated and identified. However, news of the new element was not disclosed until after the end of World War II. Most unusually, it was first revealed by Seaborg when he appeared as the guest scientist on a radio show for children on 11 November 1945. It was officially announced the following week.

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Podcasts

Listen to Curium Podcast
Transcript :

Chemistry in its element - curium


(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 launches us deep into outer space. 

Richard Corfield 

Curium is a member of a group of elements, the transuranic elements, that - with the exception of plutonium and neptunium - do not occur naturally on Earth. Curium is a hard, brittle, silvery radioactive metal that tarnishes slowly and which can only be produced in nuclear reactors. The isotope 242Cu was produced in 1944 by Glenn T Seaborg, Ralph A James and Albert Ghioso by bombarding 239Pu with alpha particles in the 60-inch Cyclotron at Berkeley University in the US. Like another synthetic element, americium, the discovery of curium was intimately bound up with the work of the Manhattan Project which Seaborg and his team were working on at the time of their discovery. This meant that neither curium nor americium could be announced to the world until after the end of the war. Seaborg revealed their discovery in November 1945 on the American TV show Quiz Kids just five days before the official unveiling of the new elements at a meeting of the American Chemical Society. 

Curium is named in honour of Pierre and Marie Curie, who pioneered the study of radioactivity in the final days of the 19th century. Nineteen radioisotopes of curium are known to exist, the first of which, 242Cu was isolated in the hydroxide form in 1947 and in its elemental form in 1951. The most stable radioisotope is 247Cm which has a half-life of 1.56 × 107 years. 248Cm has a half-life of 3.40 × 105 years, 250Cm a half-life of 9000 years, and 245Cm a half-life of 8500 years. All of the remaining radioactive isotopes have half-lives with a duration that less than 30 years, and the majority of these have half-lives that are less than a month. 

Curium has two main uses: as a fuel for Radioisotope Thermal Generators (RTGs) on board satellites, deep space probes, planetary surface rovers and in heart pacemakers, and as a alpha emitter for alpha particle X-Ray spectrometry, again particularly in space applications. 

RTGs are electrical generators which produce power from radioactive decay. Usually heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect -where an electrical current is generated at the junctions between two different metals - using an array of thermocouples. However, in some cases such as the Mars Exploration Rovers, the power is used directly to warm the vehicle. For spaceflight use, the fuel must be radioactive enough to produce large quantities of energy per unit of mass and volume. 242Cu produces about 3W of heat energy from radioactive decay per gram which compares favourably with the plutonium and americium sources commonly used in other Radioisotope Thermal Generator applications. 

Alpha Particle X-Ray Spectrometers (APXS) are devices that analyse the chemical element composition of a sample from back-scattered alpha particles. Using Rutherford's calculations of the conservation of nuclear energy and linear momentum it is possible to calculate the mass of the nucleus hit by the alpha particle and from this the energy spectrum of the material being analysed. Alpha Particle X-Ray Spectrometers tend to be confined to chemical analyses required during space missions since, although curium is both compact and power efficient, it is also a hazardous radioactive material. APXSs have a long history in space exploration being first used during the later Surveyor (Surveyor 5-7) missions that immediately preceded the Apollo Moon landings. Since the days of Surveyor alpha particle analysers have been included on many other missions including Mars Pathfinder, Mars 96, the Rosetta mission to the comet Comet 67 P/Churyumov- Gerasimenko and the Mars Exploration Rovers. 

Back on Earth most curium found in the environment today was generated by the atmospheric testing of nuclear weapons, which ceased worldwide by 1980. More localised pockets of curium contamination have occurred through accidents at weapons production facilities. 

As already mentioned, curium is hazardous. It becomes concentrated in bone marrow and because of its significant alpha activity can induce cancers. 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 

So, a crucial element in the field of space exploration. That was science writer Richard Corfield bringing us the radio active chemistry of curium. Now next week, the element named after the creator of the Periodic Table. 

Hayley Birch 

Brought up in Russia, Mendeleev was the sort of person who, it seems, was incapable of sticking to one discipline and as well as serving as the director of the Russian institute for weights and measures, had a hand in developing the Russian oil industry. Given all this, it's perhaps less surprising than it ought to be that he conceived of the Periodic Table on the same day that he was supposed to be inspecting a cheese factory. 

Meera Senthilingam 

So, quite the multi tasker. And to find out the creation, chemistry and history of the Element named after Mendeleev, Mendelevium, join Hayley Birch 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.