Twenty isotopes of californium are known ( mass number ranging from 237 to 256 ) the most stable are 251Cf with half-life 898 years, 249Cf with half-life 351 years, 250Cf with half-life 13.08 years, and 252Cf with half-life 2.645 years. Californium is the heaviest actinide to exhibit covalent properties, as is observed in the californium borate. The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate, or hydroxide. Attempts to reduce or oxidize the +3 ion in solution have failed. Ĭalifornium is only water-soluble as the californium(III) cation. Californium reacts when heated with hydrogen, nitrogen, or a chalcogen (oxygen family element) reactions with dry hydrogen and aqueous mineral acids are rapid. The element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added. Compounds in the +4 oxidation state are strong oxidizing agents and those in the +2 state are strong reducing agents. Its chemical properties are predicted to be similar to other primarily 3+ valence actinide elements and the element dysprosium, which is the lanthanide above californium in the periodic table. It typically forms eight or nine bonds to surrounding atoms or ions.
Chemical properties and compounds įurther information: Californium compounds Representative californium compounds stateĬalifornium exhibits oxidation states of 4, 3, or 2. Californium's bulk modulus is 50 ±5 GPa, which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium (70 GPa). The bulk modulus of a material is a measure of its resistance to uniform pressure. At 48 GPa of pressure the β form changes into an orthorhombic crystal system due to delocalization of the atom's 5f electrons, which frees them to bond. The α form exists below 600–800 ☌ with a density of 15.10 g/cm 3 and the β form exists above 600–800 ☌ with a density of 8.74 g/cm 3. The element has two crystalline forms at standard atmospheric pressure: a double- hexagonal close-packed form dubbed alpha (α) and a face-centered cubic form designated beta (β). It forms alloys with lanthanide metals but little is known about the resulting materials. Below 51 K (−222 ☌ −368 ☏) californium metal is either ferromagnetic or ferrimagnetic (it acts like a magnet), between 48 and 66 K it is antiferromagnetic (an intermediate state), and above 160 K (−113 ☌ −172 ☏) it is paramagnetic (external magnetic fields can make it magnetic). Californium metal starts to vaporize above 300 ☌ (570 ☏) when exposed to a vacuum. The pure metal is malleable and is easily cut with a razor blade. 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.Ĭharacteristics Physical properties Ĭalifornium is a silvery-white actinide metal with a melting point of 900 ± 30 ☌ (1,650 ± 50 ☏) and an estimated boiling point of 1,743 K (1,470 ☌ 2,680 ☏). 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. 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. Most of these applications exploit the property of certain isotopes of californium to emit neutrons. 252Cf, with a half-life of about 2.645 years, is the most common isotope used and is produced at Oak Ridge National Laboratory in the United States and Research Institute of Atomic Reactors in Russia.Ĭalifornium is one of the few transuranium elements with practical applications. This short half-life means the element is not found in significant quantities in the Earth's crust. The most stable of californium's twenty known isotopes is californium-251, with a half-life of 898 years. Californium compounds are dominated by the +3 oxidation state. Californium slowly tarnishes in air at room temperature. Two crystalline forms exist for californium at normal pressure: one above and one below 900 ☌ (1,650 ☏). The element was named after the university and the U.S. It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all elements that have been produced in amounts large enough to see with the naked eye (after einsteinium). The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding curium with alpha particles ( helium-4 ions). 1743 K (1470 ☌, 2678 ☏) (estimation) Ĭalifornium is a radioactive chemical element with the symbol Cf and atomic number 98.
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