Curium

Curium, 96Cm
Curium
Pronunciation/ˈkjʊəriəm/ (KURE-ee-əm)
Appearancesilvery metallic, glows purple in the dark
Mass number[247]
Curium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Gd

Cm

(Upn)
americiumcuriumberkelium
Atomic number (Z)96
Groupf-block groups (no number)
Periodperiod 7
Block  f-block
Electron configuration[Rn] 5f7 6d1 7s2
Electrons per shell2, 8, 18, 32, 25, 9, 2
Physical properties
Phase at STPsolid
Melting point1613 K ​(1340 °C, ​2444 °F)
Boiling point3383 K ​(3110 °C, ​5630 °F)
Density (near r.t.)13.51 g/cm3
Heat of fusion13.85 kJ/mol
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1788 1982
Atomic properties
Oxidation states+3, +4, +5,[1] +6[2] (an amphoteric oxide)
ElectronegativityPauling scale: 1.3
Ionization energies
  • 1st: 581 kJ/mol
Atomic radiusempirical: 174 pm
Covalent radius169±3 pm
Color lines in a spectral range
Spectral lines of curium
Other properties
Natural occurrencesynthetic
Crystal structuredouble hexagonal close-packed (dhcp)
Double hexagonal close packed crystal structure for curium
Electrical resistivity1.25 µΩ⋅m[3]
Magnetic orderingantiferromagnetic-paramagnetic transition at 52 K[3]
CAS Number7440-51-9
History
Namingnamed after Marie Skłodowska-Curie and Pierre Curie
DiscoveryGlenn T. Seaborg, Ralph A. James, Albert Ghiorso (1944)
Isotopes of curium
Main isotopes[4] Decay
abun­dance half-life (t1/2) mode pro­duct
242Cm synth 162.8 d α 238Pu
SF
34Si 208Pb
243Cm synth 29.1 y α 239Pu
ε 243Am
SF
244Cm synth 18.11 y α 240Pu
SF
245Cm synth 8250 y α 241Pu
SF
246Cm synth 4760 y α 242Pu
SF
247Cm synth 1.56×107 y α 243Pu
248Cm synth 3.480×105 y α 244Pu
SF
250Cm synth 8300 y SF
α 246Pu
β 250Bk
 Category: Curium
| references

Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium (the isotope 239Pu) with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.

Curium is a hard, dense, silvery metal with a high melting and boiling point for an actinide. It is paramagnetic at ambient conditions, but becomes antiferromagnetic upon cooling, and other magnetic transitions are also seen in many curium compounds. In compounds, curium usually has valence +3 and sometimes +4; the +3 valence is predominant in solutions. Curium readily oxidizes, and its oxides are a dominant form of this element. It forms strongly fluorescent complexes with various organic compounds, but there is no evidence of its incorporation into bacteria and archaea. If it gets into the human body, curium accumulates in bones, lungs, and liver, where it promotes cancer.

All known isotopes of curium are radioactive and have small critical mass for a nuclear chain reaction. They mostly emit α-particles; radioisotope thermoelectric generators can use the heat from this process, but this is hindered by the rarity and high cost of curium. Curium is used in making heavier actinides and the 238Pu radionuclide for power sources in artificial cardiac pacemakers and RTGs for spacecraft. It served as the α-source in the alpha particle X-ray spectrometers of several space probes, including the Sojourner, Spirit, Opportunity, and Curiosity Mars rovers and the Philae lander on comet 67P/Churyumov–Gerasimenko, to analyze the composition and structure of the surface.

  1. ^ Kovács, Attila; Dau, Phuong D.; Marçalo, Joaquim; Gibson, John K. (2018). "Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States". Inorg. Chem. 57 (15). American Chemical Society: 9453–9467. doi:10.1021/acs.inorgchem.8b01450. OSTI 1631597. PMID 30040397. S2CID 51717837.
  2. ^ Domanov, V. P.; Lobanov, Yu. V. (October 2011). "Formation of volatile curium(VI) trioxide CmO3". Radiochemistry. 53 (5). SP MAIK Nauka/Interperiodica: 453–6. doi:10.1134/S1066362211050018. S2CID 98052484.
  3. ^ a b Schenkel, R. (1977). "The electrical resistivity of 244Cm metal". Solid State Communications. 23 (6): 389. Bibcode:1977SSCom..23..389S. doi:10.1016/0038-1098(77)90239-3.
  4. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.