Compounds of californium
Encyclopedia
Few compounds of californium
have been made and studied. The only californium ion
that is stable in aqueous solution
s is the californium(III) cation. The other two oxidation state
s are IV (strong oxidizing agent
s) and II (strong reducing agent
s). The element forms a water-soluble chloride
, nitrate
, perchlorate
, and sulfate
and is precipitated as a fluoride
, oxalate
or hydroxide
. If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.
The +3 oxidation state is represented by californium(III) oxide (yellow-green, Cf2O3), californium(III) fluoride (bright green, CfF3) and californium(III) iodide (lemon yellow, CfI3). Other +3 oxidation states include the sulfide and metallocene
. Californium(IV) oxide (black brown, CfO2), californium(IV) fluoride (green, CfF4) represent the IV oxidation state. The II state is represented by californium(II) bromide (yellow, CfBr2) and californium(II) iodide (dark violet, CfI2).
, the distance between unit cells in the crystal, of 531.0 ± 0.2 pm
. Crystals of californium(III) oxide normally have a body-centered cubic symmetry. They convert to a monoclinic
form upon heating to about 1400 °C and melt at 1750 °C.
Californium(III) chloride (CfCl3) is an emerald green compound with a hexagonal structure that can be prepared by reacting Cf2O3 with hydrochloric acid
at 500 °C. CfCl3 is then used as a feeder stock to form the yellow-orange triiodide CfI3, which in turn can be reduced to the lavender-violet diiodide CfI2.
Californium(III) fluoride (CfF3) is a yellow-green solid with a crystal symmetry that gradually changes from orthorhombic
to trigonal when heated above room temperature. Californium(IV) fluoride (CfF4) is a bright green solid with a monoclinic crystal structure.
Californium(II) iodide (CfI2) is a deep purple solid with a stable rhombohedral structure at room temperature and an unstable hexagonal structure. Californium(III) iodide (CfI3) is a lemon-yellow solid that has a rhombohedral structure and sublimes at ~800 °C.
Californium(III) oxyfluoride (CfOF) is prepared by hydrolysis
of californium(III) fluoride (CfF3) at high temperature. Californium(III) oxychloride (CfOCl) is prepared by hydrolysis of the hydrate
of californium(III) chloride at 280–320 °C.
Heating the sulfate in air at about 1200 °C and then reducing with hydrogen at 500 °C produces the sesquioxide (Cf2O3). The hydroxide
Cf(OH)3 and the trifluoride CfF3 are slightly soluble
.
Californium(III) oxychloride
(CfOCl) was the first californium compound ever discovered.
Californium
Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made in the laboratory in 1950 by bombarding curium with alpha particles at the University of California, Berkeley. It is the ninth member of the actinide series and was the...
have been made and studied. The only californium ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
that is stable in aqueous solution
Aqueous solution
An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending aq to the relevant formula, such as NaCl. The word aqueous means pertaining to, related to, similar to, or dissolved in water...
s is the californium(III) cation. The other two oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
s are IV (strong oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...
s) and II (strong reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
s). The element forms a water-soluble chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
, nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
, perchlorate
Perchlorate
Perchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are used extensively within the pyrotechnics industry, and ammonium perchlorate is also a...
, and sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
and is precipitated as a fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
, oxalate
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...
or hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
. If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.
The +3 oxidation state is represented by californium(III) oxide (yellow-green, Cf2O3), californium(III) fluoride (bright green, CfF3) and californium(III) iodide (lemon yellow, CfI3). Other +3 oxidation states include the sulfide and metallocene
Metallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride...
. Californium(IV) oxide (black brown, CfO2), californium(IV) fluoride (green, CfF4) represent the IV oxidation state. The II state is represented by californium(II) bromide (yellow, CfBr2) and californium(II) iodide (dark violet, CfI2).
Compounds
Californium(IV) oxide (CfO2) is a black-brown solid that has a cubic crystal structure with a lattice parameterLattice constant
The lattice constant [or lattice parameter] refers to the constant distance between unit cells in a crystal lattice. Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c. However, in the special case of cubic crystal structures, all of the constants are...
, the distance between unit cells in the crystal, of 531.0 ± 0.2 pm
Picometre
A picometre is a unit of length in the metric system, equal to one trillionth, i.e. of a metre, which is the current SI base unit of length...
. Crystals of californium(III) oxide normally have a body-centered cubic symmetry. They convert to a monoclinic
Monoclinic crystal system
In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a...
form upon heating to about 1400 °C and melt at 1750 °C.
Californium(III) chloride (CfCl3) is an emerald green compound with a hexagonal structure that can be prepared by reacting Cf2O3 with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
at 500 °C. CfCl3 is then used as a feeder stock to form the yellow-orange triiodide CfI3, which in turn can be reduced to the lavender-violet diiodide CfI2.
Californium(III) fluoride (CfF3) is a yellow-green solid with a crystal symmetry that gradually changes from orthorhombic
Orthorhombic crystal system
In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...
to trigonal when heated above room temperature. Californium(IV) fluoride (CfF4) is a bright green solid with a monoclinic crystal structure.
Californium(II) iodide (CfI2) is a deep purple solid with a stable rhombohedral structure at room temperature and an unstable hexagonal structure. Californium(III) iodide (CfI3) is a lemon-yellow solid that has a rhombohedral structure and sublimes at ~800 °C.
Californium(III) oxyfluoride (CfOF) is prepared by hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of californium(III) fluoride (CfF3) at high temperature. Californium(III) oxychloride (CfOCl) is prepared by hydrolysis of the hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
of californium(III) chloride at 280–320 °C.
Heating the sulfate in air at about 1200 °C and then reducing with hydrogen at 500 °C produces the sesquioxide (Cf2O3). The hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
Cf(OH)3 and the trifluoride CfF3 are slightly soluble
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
.
Californium(III) oxychloride
Californium oxychloride
Californium oxychloride [CfOCl] is a radioactive compound first discovered in measurable quantities in 1960. It is composed of a single californium atom, and one oxychloride group. It was the first californium compound ever isolated....
(CfOCl) was the first californium compound ever discovered.