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Actinium (Ac)

Actinium

History

According to the Royal Society of Chemistry, this element was discovered in 1899 by André Debierne at Paris. He extracted it from the uranium ore pitchblende (uranium oxide, U3O8) in which it occurs in trace amounts. In 1902, Friedrich Otto Giesel independently extracted it from the same mineral and, unaware it was already known, gave it the named emanium.

Did you know?

  1. Actinium is a very powerful source of alpha rays, but is rarely used outside research.
  2. Actinium is a soft, silvery-white radioactive metal. It glows blue in the dark because its intense radioactivity excites the air around it.
  3. Actinium extracted from uranium ores is the isotope actinium-227 which has half-life of 21.7 years. It occurs naturally as one of the sequence of isotopes that originate with the radioactive decay of uranium-235. A tonne of pitchblende contains around 150 mg of actinium.
  • Atomic Properties
    Atomic number 89
    Atomic radius - Goldschmidt ( nm ) 0.203
    Atomic weight ( amu ) 227.03
    Crystal structure Face centered cubic
    Electronic structure Rn 6d1 7s2
    Ionisation potential No. eV
    1 6.9
    2 12.1
    Valences shown 0, 3
  • Physical Properties
    Boiling point ( C ) 3200 ± 300
    Density @20C ( g cm-3 ) 10.07
    Melting point ( C ) 1230
  • Thermal Properties
    Latent heat of evaporation ( J g-1 ) 1290
    Latent heat of fusion ( J g-1 ) 62.55
    Thermal conductivity @0-100C ( W m-1 K-1 ) 12
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Thorium (Th)

Thorium

About

Thorium was discovered in 1829 by J.J. Berzelius in Stockholm.

Thorium is a dark grey, radioactive metal of which the principal source is the ore, monazite, a complex phosphate of thorium, uranium, cerium and lanthanides. The metal is soft and ductile and is extracted by precipitation as the hydroxide, along with cerium and uranium; separation is achieved by further extraction with tributyl phosphate from an acid solution. The metal is made by calcium reduction of the oxide or fluoride, and pure thorium can be obtained by decomposing ThI4 on a hot filament (the Van Arkel process).

Did you know?

  1. Thorium can be used as a source of nuclear power. It is about three times as abundant as uranium and about as abundant as lead, and there is probably more energy available from thorium than from both uranium and fossil fuels. India and China are in the process of developing nuclear power plants with thorium reactors, but this is still a very new technology.
  2. The radioactivity of thorium was first demonstrated in 1898 by Gerhard Schmidt and confirmed by Marie Curie. Thorium, like uranium, survives on Earth because it has isotopes with long half-lives, such as the predominant one, thorium-232, whose half life is 14 billion years.
  3. Thorium dioxide was formerly added to glass during manufacture to increase the refractive index, producing thoriated glass for use in high-quality camera lenses.
  • Atomic Properties
    Atomic number 90
    Atomic radius - Goldschmidt ( nm ) 0.180
    Atomic weight ( amu ) 232.0381
    Crystal structure Face centred cubic
    Electronic structure Rn 6d2 7s2
    Ionisation potential No. eV
    1 6.95
    2 11.5
    3 20.0
    4 28.8
    Natural isotope distribution Mass No. %
    232 100
    Photo-electric work function ( eV ) 3.5
    Thermal neutron absorption cross-section ( Barns ) 7.4
    Valences shown 2, 3, 4
  • Electrical Properties
    Electrical resistivity @20C ( µOhmcm ) 14.0
    Temperature coefficient @0-100C ( K-1 ) 0.0040
    Superconductivity critical temperature ( K ) 1.38
    Thermal emf against Pt (cold 0C - hot 100C) ( mV ) -0.13
  • Mechanical Properties
    Material condition Soft Hard Polycrystalline
    Bulk modulus ( GPa )     54
    Hardness - Vickers 38 70
    Izod toughness ( J m-1 ) 41 6
    Poisson's ratio     0.26
    Tensile modulus ( GPa )     78.3
    Tensile strength ( MPa ) 115 305
    Yield strength ( MPa ) 48 295
  • Physical Properties
    Boiling point ( C ) 4790
    Density @20C ( g cm-3 ) 11.72
    Melting point ( C ) 1750
  • Thermal Properties
    Coefficient of thermal expansion @0-100C ( x10-6 K-1 ) 11.2
    Latent heat of evaporation ( J g-1 ) 2202
    Latent heat of fusion ( J g-1 ) 82.8
    Specific heat @25C ( J K-1 kg-1 ) 113
    Thermal conductivity @0-100C ( W m-1 K-1 ) 54

Our Products

Click below to buy this element. We stock and supply the following standard forms:

  • foil
  • wire
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Protactinium (Pa)

Protactinium

History

According to the Royal Society of Chemistry, Mendeleev said there should be an element between thorium and uranium, but it evaded detection. Then, in 1900, William Crookes separated an intensely radioactive material from uranium, but did not identify it. In 1913, Kasimir Fajans and Otto Göhring showed that this new element decayed by beta-emission and it existed only fleetingly. We now know it is a member of the sequence of elements through which uranium decays. It was the isotope protactinium-234, which has a half-life of 6 hours 42 minutes.

Did you know?

  1. Small amounts of protactinium are found naturally in uranium ores. It is also found in spent fuel rods from nuclear reactors, from which it is extracted.
  2. A longer-lived isotope was separated from the uranium ore pitchblende (uranium oxide, U3O8) in 1918 by Lise Meitner at the Kaiser-Wilhelm Institute in Berlin. This was the longer-lived isotope protactinium-231, also coming from uranium, and its half-life is 32,500 years.
  3. In 1934, Aristid von Grosse reduced protactinium oxide to protactinium metal by decomposing its iodide (PaF5) on a heated filament.
  • Atomic Properties
    Atomic number 91
    Atomic radius - Goldschmidt ( nm ) 0.161
    Atomic weight ( amu ) 231.04
    Electronic structure Rn 5f2 6d1 7s2
    Natural isotope distribution Mass No. %
    1 100
    Valences shown 4, 5
  • Physical Properties
    Density @27C ( g cm-3 ) 15.4
    Density @20C ( g cm-3 ) 10.07
    Melting point ( C ) 1230
  • Thermal Properties
    Latent heat of evaporation ( J g-1 ) 2050
    Latent heat of fusion ( J g-1 ) 72.3
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Uranium (U)

Uranium

History

Uranium was discovered in 1789 by M.H. Klaproth in Berlin, Germany.

Although uranium is the longest known member of the actinide group of metals, it attracted scant attention until the discovery of uranium fission in 1939. It is now of vital importance as a nuclear fuel. Uranium occurs naturally as two main isotopes, 238U (99.3%) and 235U (0.7%), along with a trace of a third isotope, 233U. Separation of the isotopes is achieved by conversion to the hexafluorides. The 235U isotope is the more important as this reacts with a neutron by fission to form lighter nuclei, the reaction being accompanied by the release of a considerable amount of energy and more neutrons which, in turn, fission more 235U and permits the build up of a chain reaction. The energy released as a result of this nuclear process is the order of a million times greater than that resulting from burning fossil fuel and it is for this reason that there is substantial interest in nuclear fission.

238U is also important in a nuclear reactor as it can absorb neutrons itself to produce heavier elements, the most important of which is plutonium, another nuclear fuel. Under the correct conditions, more plutonium can be produced from 238U than the amount of 235U consumed, and such an arrangement is found in a "breeder" type of nuclear reactor.

Did you know?

  1. Uranium is a very important element because it provides us with nuclear fuel used to generate electricity in nuclear power stations. It is also the major material from which other synthetic transuranium elements are made.
  2. Naturally occurring uranium consists of 99% uranium-238 and 1% uranium-235. Uranium-235 is the only naturally occurring fissionable fuel (a fuel that can sustain a chain reaction). Uranium fuel used in nuclear reactors is enriched with uranium-235. The chain reaction is carefully controlled using neutron-absorbing materials. The heat generated by the fuel is used to create steam to turn turbines and generate electrical power.
  3. Depleted uranium is uranium that has much less uranium-235 than natural uranium. It is considerably less radioactive than natural uranium. It is a dense metal that can be used as ballast for ships and counterweights for aircraft. It is also used in ammunition and armour.
  • Atomic Properties
    Atomic number 92
    Atomic radius - Goldschmidt ( nm ) 0.138
    Atomic weight ( amu ) 238.0289
    Crystal structure Orthorhombic
    Electronic structure Rn 5f3 6d1 7s2
    Ionisation potential No. eV
    1 6.19
    Natural isotope distribution Mass No. %
    234 0.005
    235 0.720
    238 99.275
    Photo-electric work function ( eV ) 3.6
    Thermal neutron absorption cross-section ( Barns ) 7.6
    Valences shown 2, 3, 4, 5, 6
  • Electrical Properties
    Electrical resistivity @20C ( µOhmcm ) 27
    Temperature coefficient @0-100C ( K-1 ) 0.0034
  • Mechanical Properties
    Material condition Soft Hard Polycrystalline
    Bulk modulus ( GPa )     97.9
    Hardness - Vickers 187 250
    Izod toughness ( J m-1 ) 19 15
    Poisson's ratio     0.20
    Tensile modulus ( GPa )     175.8
    Tensile strength ( MPa ) 385 580
    Yield strength ( MPa ) 190 250
  • Physical Properties
    Boiling point ( C ) 3818
    Density @20C ( g cm-3 ) 19.05
    Melting point ( C ) 1132
  • Thermal Properties
    Coefficient of thermal expansion @0-100C ( x10-6 K-1 ) 13.4
    Latent heat of evaporation ( J g-1 ) 1753
    Latent heat of fusion ( J g-1 ) 52.5
    Specific heat @25C ( J K-1 kg-1 ) 116
    Thermal conductivity @0-100C ( W m-1 K-1 ) 27.5

Our Products

Click below to buy this element. We stock and supply the following standard forms:

  • sputteringtarget
  • wire
  • foil
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Neptunium (Np)

Neptunium

History

According to the Royal Society of Chemistry, in early 1934, Enrico Fermi in Italy tried to produce elements 93 and 94 by bombarding uranium with neutrons, and claimed success. Ida Tacke-Noddack questioned Fermi’s claim, pointing out he had failed to do a complete analysis, and all that he had found were fission products of uranium. (Fermi had in fact discovered nuclear fission but not realised it.)

Did you know?

  1. In 1938, Horia Hulubei and Yvette Cauchois claimed to have discovered element 93, but the claim was also criticised on the grounds that element 93 did not occur naturally.
  2. Neptunium was first made in 1940 by Edwin McMillan and Philip Abelson at Berkeley, California. It came from a uranium target that had been bombarded with slow neutrons and which then emitted unusual beta-rays indicating a new isotope. Abelson proved there was indeed a new element present.
  • Atomic Properties
    Atomic number 93
    Atomic radius - Goldschmidt ( nm ) 0.15
    Atomic weight ( amu ) 237.05
    Electronic structure Rn 5f4 6d1 7s2
    Ionisation potential No. eV
    1 6.16
    Thermal neutron absorption cross-section ( Barns ) 170
    Valences shown 3, 4, 5, 6
  • Physical Properties
    Boiling point ( C ) 3902
    Density @20C ( g cm-3 ) 20.4
    Melting point ( C ) 640
  • Thermal Properties
    Latent heat of evaporation ( J g-1 ) 1420
    Latent heat of fusion ( J g-1 ) 39.8
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Plutonium (Pu)

Plutonium

History

Plutonium was first made in December 1940 at Berkeley, California, by Glenn Seaborg, Arthur Wahl, Joseph Kennedy, and Edwin McMillan. They produced it by bombarding uranium-238 with deuterium nuclei (alpha particles).

This first produced neptunium-238 with a half-life of two days, and this decayed by beta emission to form element 94 (plutonium). Within a couple of months element 94 had been conclusively identified and its basic chemistry shown to be like that of uranium.

To begin with, the amounts of plutonium produced were invisible to the eye, but by August 1942 there was enough to see and weigh, albeit only 3 millionths of a gram. However, by 1945 the Americans had several kilograms, and enough plutonium to make three atomic bombs, one of which exploded over Nagasaki in August 1945.

Did you know?

  1. Plutonium was used in several of the first atomic bombs, and is still used in nuclear weapons. The complete detonation of a kilogram of plutonium produces an explosion equivalent to over 10,000 tonnes of chemical explosive.
  2. Plutonium is also a key material in the development of nuclear power. It has been used as a source of energy on space missions, such as the Mars Curiosity Rover and the New Horizons spacecraft on its way to Pluto.
  3. The greatest source of plutonium is the irradiation of uranium in nuclear reactors. This produces the isotope plutonium-239, which has a half-life of 24,400 years.
  • Atomic Properties
    Atomic number 94
    Atomic radius - Goldschmidt ( nm ) 0.162
    Atomic weight ( amu ) (244)
    Electronic structure Rn 5f6 7s2
    Ionisation potential No. eV
    1 5.8
    Valences shown 3, 4, 5, 6
  • Electrical Properties
    Electrical resistivity @22C ( µOhmcm ) 146
  • Physical Properties
    Boiling point ( C ) 3235
    Density @19.8C ( g cm-3 )
    Melting point ( C ) 640
  • Thermal Properties
    Coefficient of thermal expansion @0-100C ( x10-6 K-1 ) 55
    Latent heat of evaporation ( J g-1 ) 1428
    Latent heat of fusion ( J g-1 ) 11.5
    Thermal conductivity @0-100C ( W m-1 K-1 ) 8.4
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Americium (Am)

Americium

History

This element was in fact discovered after curium, the element which follows it in the periodic table. However, it did once exist on Earth having been produced for millions of years in natural nuclear reactors in Oklo, Gabon. These ceased to function a billion years ago, and as the longest lived isotope is americium-247, with a half-life of 7370 years, none has survived to the present day.

Americium was first made late in 1944 at the University of Chicago by a team which included Glenn Seaborg, Ralph James, Leon Morgan, and Albert Ghiorso. The americium was produced by bombarding plutonium with neutrons in a nuclear reactor. This produced isotope americium-241, which has a half-life of this is 432 years.

Did you know?

  1. Americium is commonly used in smoke alarms, but has few other uses.
  2. It has the potential to be used in spacecraft batteries in the future. Currently plutonium is used but availability is poor so alternatives are being considered.
  3. It is of interest as part of the decay sequence that occurs in nuclear power production.
  • Atomic Properties
    Atomic number 95
    Atomic radius - Goldschmidt ( nm ) 0.182
    Atomic weight ( amu ) (243)
    Crystal structure Face centered cubic
    Electronic structure Rn 5f7 7s2
    Ionisation potential No. eV
    1 6.0
    Valences shown 3, 4, 5, 6
  • Electrical Properties
    Electrical resistivity @27C ( µOhmcm ) 68.9
    Superconductivity critical temperature ( K ) 1.06
  • Thermal Properties
    Latent heat of evaporation ( J g-1 ) 980
    Latent heat of fusion ( J g-1 ) 59.3
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Curium (Cm)

Curium

History

According to the Royal Society of Chemistry, 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.

Did you know?

  1. A tiny sample of curium was eventually separated and sent to the Metallurgical Laboratory at the University of Chicago where it was 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.
  • Atomic Properties
    Atomic number 96
    Atomic radius - Goldschmidt ( nm ) 0.174
    Atomic weight ( amu ) (247)
    Electronic structure Rn 5f7 6d1 7s2
    Valences shown 3
  • Physical Properties
    Density @27C ( g cm-3 ) 13.5
    Melting point ( C ) 1340 ±40
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Berkelium (Bk)

Berkelium

History

Berkelium was first produced in December 1949, at the University of California at Berkeley, and was made by Stanley Thompson, Albert Ghiorso, and Glenn Seaborg. They took americium-241, which had first been made in 1944, and bombarded it with helium nuclei (alpha particles) for several hours in the 60-inch cyclotron. The americium itself had been produced by bombarding plutonium with neutrons.

The Berkeley team dissolved the target in acid and used ion exchange to separate the new elements that had been created. This was the isotope berkelium-243 which has a half-life of about 5 hours. It took a further nine years before enough berkelium had been made to see with the naked eye, and even this was only a few micrograms. The first chemical compound, berkelium dioxide, BkO2, was made in 1962.

Did you know?

  1. Less than a gram of berkelium is made each year. It is made in nuclear reactors by the neutron bombardment of plutonium-239.
  • Atomic Properties
    Atomic number 97
    Atomic weight ( amu ) (247)
    Electronic structure Rn 5f9 s2
    Valences shown 3, 4
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Californium (Cf)

Californium

History

Californium was first made in 1950 at Berkeley, California, by a team consisting of Stanley Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn Seaborg. They made it by firing helium nuclei (alpha particles) at curium-242. The process yielded the isotope californium-245 which has a half-life of 44 minutes. Curium is intensely radioactive and it had taken the team three years to collect the few milligrams needed for the experiment, and even so only a few micrograms of this were used. Their endeavours produced around 5,000 atoms of californium, but there was enough to show it really was a new element.

Did you know?

  1. Californium is a very strong neutron emitter. It is used in portable metal detectors, for identifying gold and silver ores, to identify water and oil layers in oil wells and to detect metal fatigue and stress in aeroplanes.
  • Atomic Properties
    Atomic number 98
    Atomic radius - Goldschmidt ( nm ) 0.186
    Atomic weight ( amu ) (251)
    Electronic structure Rn 5f1O 7s2
    Valences shown 3, 4
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Einsteinium (Es)

Einsteinium

History

Einsteinium was discovered in the debris of the first thermonuclear explosion which took place on a Pacific atoll, on 1 November 1952. Fall-out material, gathered from a neighbouring atoll, was sent to Berkeley, California, for analysis. There it was examined by Gregory Choppin, Stanley Thompson, Albert Ghiorso, and Bernard Harvey. Within a month they had discovered and identified 200 atoms of a new element, einsteinium, but it was not revealed until 1955.

Did you know?

  1. The einsteinium had formed when some uranium atoms had captured several neutrons and gone through a series of capture and decay steps resulting in einsteinium-253, which has a half-life of 20.5 days.
  2. By 1961, enough einsteinium had been collected to be visible to the naked eye, and weighed, although it amounted to mere 10 millionths of a gram.
  • Atomic Properties
    Atomic number 99
    Atomic radius - Goldschmidt ( nm ) 0.186
    Atomic weight ( amu ) (252)
    Electronic structure Rn 5f11 7s2
    Valences shown 2, 3
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Fermium (Fm)

Fermium

History

According to the Royal Society of Chemistry, 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.

Did you know?

  1. 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.
  2. Fermium can be obtained, in microgram quantities, from the neutron bombardment of plutonium in a nuclear reactor.
  • Atomic Properties
    Atomic number 100
    Atomic weight ( amu ) (257)
    Electronic structure Rn 5f12 7s2
    Valences shown 1
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Medelevium (Md)

Medelevium

History

According to the Royal Society of Chemistry, seventeen atoms of mendelevium were made in 1955 by Albert Ghiorso, Bernard Harvey, Gregory Chopin, Stanley Thompson, and Glenn Seaborg. They were produced during an all-night experiment using the cyclotron at Berkeley, California.

In this, a sample of einsteinium-253 was bombarded with alpha-particles (helium nuclei) and mendelevium-256 was detected. This had a half-life of around 78 minutes. Further experiments yielded several thousand atoms of mendelevium, and today it is possible to produce millions of them.

Did you know?

  1. The longest lived isotope is mendelevium-260 which has a half-life of 28 days.
  2. It can only be produced in particle accelerators by bombarding lighter elements with charged particles. A total of sixteen mendelevium isotopes are known, the most stable being 258Md with a half-life of 51 days; nevertheless, the shorter-lived 256Md (half-life 1.17 hours) is most commonly used in chemistry because it can be produced on a larger scale.
  • Atomic Properties
    Atomic number 101
    Atomic weight ( amu ) (258)
    Electronic structure Rn 5f13 7s2
    Valences shown 2, 3
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Nobelium (No)

Nobelium

History

According to the Royal Society of Chemistry, this element’s history is one of controversy. In 1956, a team led by Georgy Flerov at the Institute of Atomic Energy, Moscow, synthesised element 102 by bombarding plutonium with oxygen and got atoms of element 102, isotope-252. However, they did not report their success.

In 1957, the Nobel Institute of Physics in Stockholm announced isotope-253 which had been made by bombarding curium with carbon. Then in 1958, Albert Ghiorso at the Lawrence Berkeley Laboratory (LBL) claimed isotope-254, also made by bombarding curium with carbon. These claims were challenged by the Russians.

Did you know?

  1. Nobelium is made by bombarding curium with carbon in a device called a cyclotron.
  2. In 1957, the Nobel Institute of Physics in Stockholm announced isotope-253 which had been made by bombarding curium with carbon. Then in 1958, Albert Ghiorso at the Lawrence Berkeley Laboratory (LBL) claimed isotope-254, also made by bombarding curium with carbon. These claims were challenged by the Russians.
  3. In 1962-63, the Russian Joint Institute of Nuclear Research, based at Dubna, synthesised isotopes 252 to 256. Ghiorso still insisted his group were the first to discover element 102, and so began years of recrimination, finally ending in the International Union of Pure and Applied Chemists deciding in favour of the Russians being the discoverers.
  • Atomic Properties
    Atomic number 102
    Atomic weight ( amu ) (259)
    Electronic structure Rn 5f14 7s2
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Lawrencium (Lr)

Lawrencium

History

According to the Royal Society of Chemistry, this element had a controversial history of discovery. In 1958, the Lawrence Berkeley Laboratory (LBL) bombarded curium with nitrogen and appeared to get element 103, isotope-257. In 1960, they bombarded californium with boron hoping to get isotope-259 but the results were inconclusive. In 1961, they bombarded curium with boron and claimed isotope-257.

In 1965, the Soviet Union’s Joint Institute for Nuclear Research (JINR) successfully bombarded americium with oxygen and got isotope-256. They also checked the LBL’s work, and claimed it was inaccurate. The LBL then said their product must have been isotope-258. The International Unions of Pure and Applied Chemistry awarded discovery to the LBL.

Did you know?

  1. Lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles.
  2. Twelve isotopes of lawrencium are currently known; the most stable is 266Lr with a half-life of 11 hours, but the shorter-lived 260Lr (half-life 2.7 minutes) is most commonly used in chemistry because it can be produced on a larger scale.
  • Atomic Properties
    Atomic number 103
    Atomic radius - Goldschmidt ( nm ) 0.197
    Atomic weight ( amu ) (260)
    Electronic structure Rn 5f14 6d1 7s2
    Valences shown 3