Californium

  • californium, 98cf
    a very small disc of silvery metal, magnified to show its metallic texture
    californium
    pronunciationm/ (for-nee-əm)
    appearancesilvery
    mass number[251]
    californium 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
    dy

    cf

    (upb)
    berkeliumcaliforniumeinsteinium
    atomic number (z)98
    groupgroup n/a
    periodperiod 7
    blockf-block
    element category  actinide
    electron configuration[rn] 5f10 7s2[1]
    electrons per shell2, 8, 18, 32, 28, 8, 2
    physical properties
    phase at stpsolid
    melting point1173 k ​(900 °c, ​1652 °f)[2]
    boiling point1743 k ​(1470 °c, ​2678 °f) (estimation)[3]
    density (near r.t.)15.1 g/cm3[2]
    atomic properties
    oxidation states+2, +3, +4, +5[4][5]
    electronegativitypauling scale: 1.3[6]
    ionization energies
    • 1st: 608 kj/mol[7]
    color lines in a spectral range
    spectral lines of californium
    other properties
    natural occurrencesynthetic
    crystal structuredouble hexagonal close-packed (dhcp)
    double hexagonal close packed crystal structure for californium
    mohs hardness3–4[8]
    cas number7440-71-3[2]
    history
    namingafter california, where it was discovered
    discoverylawrence berkeley national laboratory (1950)
    main isotopes of californium[9][10]
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    248cf syn 333.5 d α (100%) 244cm
    sf (2.9×10−3%)
    249cf syn 351 y α (100%) 245cm
    sf (5.0×10−7%)
    250cf syn 13.08 y α (99.92%) 246cm
    sf (0.08%)
    251cf syn 898 y α 247cm
    252cf syn 2.645 y α (96.91%) 248cm
    sf (3.09%)
    253cf syn 17.81 d β (99.69%) 253es
    α (0.31%) 249cm
    254cf syn 60.5 d sf (99.69%)
    α (0.31%) 250cm
    category category: californium
    | references

    californium is a radioactive chemical element with the symbol cf and atomic number 98. the element was first synthesized in 1950 at the lawrence berkeley national laboratory (then the university of california radiation laboratory), by bombarding curium with alpha particles (helium-4 ions). it is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). the element was named after the university and the state of california.

    two crystalline forms exist for californium under normal pressure: one above and one below 900 °c (1,650 °f). a third form exists at high pressure. californium slowly tarnishes in air at room temperature. compounds of californium are dominated by the +3 oxidation state. the most stable of californium's twenty known isotopes is californium-251, which has a half-life of 898 years. this short half-life means the element is not found in significant quantities in the earth's crust.[a] californium-252, with a half-life of about 2.645 years, is the most common isotope used and is produced at the oak ridge national laboratory in the united states and the research institute of atomic reactors in russia.

    californium is one of the few transuranium elements that have practical applications. most of these applications exploit the property of certain isotopes of californium to emit neutrons. for example, californium can be used to help start up nuclear reactors, and it is employed as a source of neutrons when studying materials using neutron diffraction and neutron spectroscopy. californium can also be used in nuclear synthesis of higher mass elements; oganesson (element 118) was synthesized by bombarding californium-249 atoms with calcium-48 ions. users of californium must take into account radiological concerns and the element's ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue.

  • characteristics
  • history
  • occurrence
  • production
  • applications
  • precautions
  • notes
  • references
  • bibliography
  • external links

Californium, 98Cf
A very small disc of silvery metal, magnified to show its metallic texture
Californium
Pronunciationm/ (FOR-nee-əm)
Appearancesilvery
Mass number[251]
Californium 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
Dy

Cf

(Upb)
berkeliumcaliforniumeinsteinium
Atomic number (Z)98
Groupgroup n/a
Periodperiod 7
Blockf-block
Element category  Actinide
Electron configuration[Rn] 5f10 7s2[1]
Electrons per shell2, 8, 18, 32, 28, 8, 2
Physical properties
Phase at STPsolid
Melting point1173 K ​(900 °C, ​1652 °F)[2]
Boiling point1743 K ​(1470 °C, ​2678 °F) (estimation)[3]
Density (near r.t.)15.1 g/cm3[2]
Atomic properties
Oxidation states+2, +3, +4, +5[4][5]
ElectronegativityPauling scale: 1.3[6]
Ionization energies
  • 1st: 608 kJ/mol[7]
Color lines in a spectral range
Spectral lines of californium
Other properties
Natural occurrencesynthetic
Crystal structuredouble hexagonal close-packed (dhcp)
Double hexagonal close packed crystal structure for californium
Mohs hardness3–4[8]
CAS Number7440-71-3[2]
History
Namingafter California, where it was discovered
DiscoveryLawrence Berkeley National Laboratory (1950)
Main isotopes of californium[9][10]
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
248Cf syn 333.5 d α (100%) 244Cm
SF (2.9×10−3%)
249Cf syn 351 y α (100%) 245Cm
SF (5.0×10−7%)
250Cf syn 13.08 y α (99.92%) 246Cm
SF (0.08%)
251Cf syn 898 y α 247Cm
252Cf syn 2.645 y α (96.91%) 248Cm
SF (3.09%)
253Cf syn 17.81 d β (99.69%) 253Es
α (0.31%) 249Cm
254Cf syn 60.5 d SF (99.69%)
α (0.31%) 250Cm
Category Category: Californium
| references

Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after the university and the state of California.

Two crystalline forms exist for californium under normal pressure: one above and one below 900 °C (1,650 °F). A third form exists at high pressure. Californium slowly tarnishes in air at room temperature. Compounds of californium are dominated by the +3 oxidation state. The most stable of californium's twenty known isotopes is californium-251, which has a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust.[a] Californium-252, with a half-life of about 2.645 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia.

Californium is one of the few transuranium elements that have practical applications. Most of these applications exploit the property of certain isotopes of californium to emit neutrons. For example, californium can be used to help start up nuclear reactors, and it is employed as a source of neutrons when studying materials using neutron diffraction and neutron spectroscopy. Californium can also be used in nuclear synthesis of higher mass elements; oganesson (element 118) was synthesized by bombarding californium-249 atoms with calcium-48 ions. Users of californium must take into account radiological concerns and the element's ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue.