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Curium

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. The most stable isotope, 247Cm, has a half-life of 15.6 million years; the longest-lived curium isotopes predominantly emit alpha 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.

History
Though curium had likely been produced in previous nuclear experiments as well as the natural nuclear fission reactor at Oklo, Gabon, it was first intentionally synthesized, isolated and identified in 1944, at University of California, Berkeley, by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso. In their experiments, they used a 60 in cyclotron.

Curium was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory), University of Chicago. It was the third transuranium element to be discovered even though it is the fourth in the series – the lighter element americium was still unknown.

The sample was prepared as follows: first plutonium nitrate solution was coated on a platinum foil of ~0.5 cm2 area, the solution was evaporated and the residue was converted into plutonium(IV) oxide (PuO2) by annealing. Following cyclotron irradiation of the oxide, the coating was dissolved with nitric acid and then precipitated as the hydroxide using concentrated aqueous ammonia solution. The residue was dissolved in perchloric acid, and further separation was done by ion exchange to yield a certain isotope of curium. The separation of curium and americium was so painstaking that the Berkeley group initially called those elements pandemonium (from Greek for all demons or hell) and delirium (from Latin for madness).

Curium-242 was made in July–August 1944 by bombarding 239Pu with α-particles to produce curium with the release of a neutron:

Curium-242 was unambiguously identified by the characteristic energy of the α-particles emitted during the decay:

The half-life of this alpha decay was first measured as 150 days and then corrected to 162.8 days.

Another isotope 240Cm was produced in a similar reaction in March 1945:

The α-decay half-life of 240Cm was correctly determined as 26.7 days.

The discovery of curium and americium in 1944 was closely related to the Manhattan Project, so the results were confidential and declassified only in 1945. Seaborg leaked the synthesis of the elements 95 and 96 on the U.S. radio show for children, the Quiz Kids, five days before the official presentation at an American Chemical Society meeting on November 11, 1945, when one listener asked if any new transuranic element beside plutonium and neptunium had been discovered during the war. The discovery of curium (242Cm and 240Cm), its production, and its compounds was later patented listing only Seaborg as the inventor.

The element was named after Marie Curie and her husband Pierre Curie, who are known for discovering radium and for their work in radioactivity. It followed the example of gadolinium, a lanthanide element above curium in the periodic table, which was named after the explorer of rare-earth elements Johan Gadolin:
 * "As the name for the element of atomic number 96 we should like to propose 'curium', with symbol Cm. The evidence indicates that element 96 contains seven 5f electrons and is thus analogous to the element gadolinium, with its seven 4f electrons in the regular rare earth series. On this basis element 96 is named after the Curies in a manner analogous to the naming of gadolinium, in which the chemist Gadolin was honored."

The first curium samples were barely visible, and were identified by their radioactivity. Louis Werner and Isadore Perlman made the first substantial sample of 30 μg curium-242 hydroxide at University of California, Berkeley in 1947 by bombarding americium-241 with neutrons. Macroscopic amounts of curium(III) fluoride were obtained in 1950 by W. W. T. Crane, J. C. Wallmann and B. B. Cunningham. Its magnetic susceptibility was very close to that of GdF3 providing the first experimental evidence for the +3 valence of curium in its compounds. Curium metal was produced only in 1951 by reduction of CmF3 with barium.

Physical
A synthetic, radioactive element, curium is a hard, dense metal with a silvery-white appearance and physical and chemical properties resembling gadolinium. Its melting point of 1344 °C is significantly higher than that of the previous elements neptunium (637 °C), plutonium (639 °C) and americium (1176 °C). In comparison, gadolinium melts at 1312 °C. Curium boils at 3556 °C. With a density of 13.52 g/cm3, curium is lighter than neptunium (20.45 g/cm3) and plutonium (19.8 g/cm3), but heavier than most other metals. Of two crystalline forms of curium, α-Cm is more stable at ambient conditions. It has a hexagonal symmetry, space group P63/mmc, lattice parameters a = 365 pm and c = 1182 pm, and four formula units per unit cell. The crystal consists of double-hexagonal close packing with the layer sequence ABAC and so is isotypic with α-lanthanum. At pressure >23 GPa, at room temperature, α-Cm becomes β-Cm, which has face-centered cubic symmetry, space group Fm$\overline{3}$m and lattice constant a = 493 pm. On further compression to 43 GPa, curium becomes an orthorhombic γ-Cm structure similar to α-uranium, with no further transitions observed up to 52 GPa. These three curium phases are also called Cm I, II and III.

Curium has peculiar magnetic properties. Its neighbor element americium shows no deviation from Curie-Weiss paramagnetism in the entire temperature range, but α-Cm transforms to an antiferromagnetic state upon cooling to 65–52 K, and β-Cm exhibits a ferrimagnetic transition at ~205 K. Curium pnictides show ferromagnetic transitions upon cooling: 244CmN and 244CmAs at 109 K, 248CmP at 73 K and 248CmSb at 162 K. The lanthanide analog of curium, gadolinium, and its pnictides, also show magnetic transitions upon cooling, but the transition character is somewhat different: Gd and GdN become ferromagnetic, and GdP, GdAs and GdSb show antiferromagnetic ordering.

In accordance with magnetic data, electrical resistivity of curium increases with temperature – about twice between 4 and 60 K – and then is nearly constant up to room temperature. There is a significant increase in resistivity over time (~$10 μΩ·cm/h$) due to self-damage of the crystal lattice by alpha decay. This makes uncertain the true resistivity of curium (~$125 μΩ·cm$). Curium's resistivity is similar to that of gadolinium, and the actinides plutonium and neptunium, but significantly higher than that of americium, uranium, polonium and thorium.

Under ultraviolet illumination, curium(III) ions show strong and stable yellow-orange fluorescence with a maximum in the range of 590–640 nm depending on their environment. The fluorescence originates from the transitions from the first excited state 6D7/2 and the ground state 8S7/2. Analysis of this fluorescence allows monitoring interactions between Cm(III) ions in organic and inorganic complexes.

Chemical
Curium ion in solution almost always has a +3 oxidation state, the most stable oxidation state for curium. A +4 oxidation state is seen mainly in a few solid phases, such as CmO2 and CmF4. Aqueous curium(IV) is only known in the presence of strong oxidizers such as potassium persulfate, and is easily reduced to curium(III) by radiolysis and even by water itself. Chemical behavior of curium is different from the actinides thorium and uranium, and is similar to americium and many lanthanides. In aqueous solution, the Cm3+ ion is colorless to pale green; Cm4+ ion is pale yellow. The optical absorption of Cm3+ ion contains three sharp peaks at 375.4, 381.2 and 396.5 nm and their strength can be directly converted into the concentration of the ions. The +6 oxidation state has only been reported once in solution in 1978, as the curyl ion : this was prepared from beta decay of americium-242 in the americium(V) ion. Failure to get Cm(VI) from oxidation of Cm(III) and Cm(IV) may be due to the high Cm4+/Cm3+ ionization potential and the instability of Cm(V).

Curium ions are hard Lewis acids and thus form most stable complexes with hard bases. The bonding is mostly ionic, with a small covalent component. Curium in its complexes commonly exhibits a 9-fold coordination environment, with a tricapped trigonal prismatic molecular geometry.

Isotopes
About 19 radioisotopes and 7 nuclear isomers, 233Cm to 251Cm, are known; none are stable. The longest half-lives are 15.6 million years (247Cm) and 348,000 years (248Cm). Other long-lived ones are 245Cm (8500 years), 250Cm (8300 years) and 246Cm (4760 years). Curium-250 is unusual: it mostly (~86%) decays by spontaneous fission. The most commonly used isotopes are 242Cm and 244Cm with the half-lives 162.8 days and 18.1 years, respectively.

All isotopes ranging from 242Cm to 248Cm, as well as 250Cm, undergo a self-sustaining nuclear chain reaction and thus in principle can be a nuclear fuel in a reactor. As in most transuranic elements, nuclear fission cross section is especially high for the odd-mass curium isotopes 243Cm, 245Cm and 247Cm. These can be used in thermal-neutron reactors, whereas a mixture of curium isotopes is only suitable for fast breeder reactors since the even-mass isotopes are not fissile in a thermal reactor and accumulate as burn-up increases. The mixed-oxide (MOX) fuel, which is to be used in power reactors, should contain little or no curium because neutron activation of 248Cm will create californium. Californium is a strong neutron emitter, and would pollute the back end of the fuel cycle and increase the dose to reactor personnel. Hence, if minor actinides are to be used as fuel in a thermal neutron reactor, the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present.

The adjacent table lists the critical masses for curium isotopes for a sphere, without moderator or reflector. With a metal reflector (30 cm of steel), the critical masses of the odd isotopes are about 3–4 kg. When using water (thickness ~20–30 cm) as the reflector, the critical mass can be as small as 59 grams for 245Cm, 155 grams for 243Cm and 1550 grams for 247Cm. There is significant uncertainty in these critical mass values. While it is usually on the order of 20%, the values for 242Cm and 246Cm were listed as large as 371 kg and 70.1 kg, respectively, by some research groups.

Curium is not currently used as nuclear fuel due to its low availability and high price. 245Cm and 247Cm have very small critical mass and so could be used in tactical nuclear weapons, but none are known to have been made. Curium-243 is not suitable for such, due to its short half-life and strong α emission, which would cause excessive heat. Curium-247 would be highly suitable due to its long half-life, which is 647 times longer than plutonium-239 (used in many existing nuclear weapons).

Occurrence
The longest-lived isotope, 247Cm, has half-life 15.6 million years; so any primordial curium, that is, present on Earth when it formed, should have decayed by now. Its past presence as an extinct radionuclide is detectable as an excess of its primordial, long-lived daughter 235U. Traces of 242Cm may occur naturally in uranium minerals due to neutron capture and beta decay (238U → 239Pu → 240Pu → 241Am → 242Cm), though the quantities would be tiny and this has not been confirmed: even with "extremely generous" estimates for neutron absorption possibilities, the quantity of 242Cm present in 1 × 108 kg of 18% uranium pitchblende would not even be one atom. Traces of 247Cm are also probably brought to Earth in cosmic rays, but again this has not been confirmed. There is also the possibility of 244Cm being produced as the double beta decay daughter of natural 244Pu.

Curium is made artificially in small amounts for research purposes. It also occurs as one of the waste products in spent nuclear fuel. Curium is present in nature in some areas used for nuclear weapons testing. Analysis of the debris at the test site of the United States' first thermonuclear weapon, Ivy Mike (1 November 1952, Enewetak Atoll), besides einsteinium, fermium, plutonium and americium also revealed isotopes of berkelium, californium and curium, in particular 245Cm, 246Cm and smaller quantities of 247Cm, 248Cm and 249Cm.

Atmospheric curium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 4,000 times higher concentration of curium at the sandy soil particles than in water present in the soil pores. An even higher ratio of about 18,000 was measured in loam soils.

The transuranium elements from americium to fermium, including curium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so.

Curium, and other non-primordial actinides, have also been suspected to exist in the spectrum of Przybylski's Star.

Isotope preparation
Curium is made in small amounts in nuclear reactors, and by now only kilograms of 242Cm and 244Cm have been accumulated, and grams or even milligrams for heavier isotopes. Hence the high price of curium, which has been quoted at 160–185 USD per milligram, with a more recent estimate at US$2,000/g for 242Cm and US$170/g for 244Cm. In nuclear reactors, curium is formed from 238U in a series of nuclear reactions. In the first chain, 238U captures a neutron and converts into 239U, which via β− decay transforms into 239Np and 239Pu.

Further neutron capture followed by β−-decay gives americium (241Am) which further becomes 242Cm:

For research purposes, curium is obtained by irradiating not uranium but plutonium, which is available in large amounts from spent nuclear fuel. A much higher neutron flux is used for the irradiation that results in a different reaction chain and formation of 244Cm:

Curium-244 alpha decays to 240Pu, but it also absorbs neutrons, hence a small amount of heavier curium isotopes. Of those, 247Cm and 248Cm are popular in scientific research due to their long half-lives. But the production rate of 247Cm in thermal neutron reactors is low because it is prone to fission due to thermal neutrons. Synthesis of 250Cm by neutron capture is unlikely due to the short half-life of the intermediate 249Cm (64 min), which β− decays to the berkelium isotope 249Bk.

The above cascade of (n,γ) reactions gives a mix of different curium isotopes. Their post-synthesis separation is cumbersome, so a selective synthesis is desired. Curium-248 is favored for research purposes due to its long half-life. The most efficient way to prepare this isotope is by α-decay of the californium isotope 252Cf, which is available in relatively large amounts due to its long half-life (2.65 years). About 35–50 mg of 248Cm is produced thus, per year. The associated reaction produces 248Cm with isotopic purity of 97%.

Another isotope, 245Cm, can be obtained for research, from α-decay of 249Cf; the latter isotope is produced in small amounts from β−-decay of 249Bk.

Metal preparation
Most synthesis routines yield a mix of actinide isotopes as oxides, from which a given isotope of curium needs to be separated. An example procedure could be to dissolve spent reactor fuel (e.g. MOX fuel) in nitric acid, and remove the bulk of the uranium and plutonium using a PUREX (Plutonium – URanium EXtraction) type extraction with tributyl phosphate in a hydrocarbon. The lanthanides and the remaining actinides are then separated from the aqueous residue (raffinate) by a diamide-based extraction to give, after stripping, a mixture of trivalent actinides and lanthanides. A curium compound is then selectively extracted using multi-step chromatographic and centrifugation techniques with an appropriate reagent. Bis-triazinyl bipyridine complex has been recently proposed as such reagent which is highly selective to curium. Separation of curium from the very chemically similar americium can also be done by treating a slurry of their hydroxides in aqueous sodium bicarbonate with ozone at elevated temperature. Both americium and curium are present in solutions mostly in the +3 valence state; americium oxidizes to soluble Am(IV) complexes, but curium stays unchanged and so can be isolated by repeated centrifugation.

Metallic curium is obtained by reduction of its compounds. Initially, curium(III) fluoride was used for this purpose. The reaction was done in an environment free of water and oxygen, in an apparatus made of tantalum and tungsten, using elemental barium or lithium as reducing agents.
 * $$\mathrm{CmF_3\ +\ 3\ Li\ \longrightarrow \ Cm\ +\ 3\ LiF}$$

Another possibility is reduction of curium(IV) oxide using a magnesium-zinc alloy in a melt of magnesium chloride and magnesium fluoride.

Oxides
Curium readily reacts with oxygen forming mostly Cm2O3 and CmO2 oxides, but the divalent oxide CmO is also known. Black CmO2 can be obtained by burning curium oxalate, nitrate , or hydroxide in pure oxygen. Upon heating to 600–650 °C in vacuum (about 0.01 Pa), it transforms into the whitish Cm2O3:

Or, Cm2O3 can be obtained by reducing CmO2 with molecular hydrogen:

Also, a number of ternary oxides of the type M(II)CmO3 are known, where M stands for a divalent metal, such as barium.

Thermal oxidation of trace quantities of curium hydride (CmH2–3) has been reported to give a volatile form of CmO2 and the volatile trioxide CmO3, one of two known examples of the very rare +6 state for curium. Another observed species was reported to behave similar to a supposed plutonium tetroxide and was tentatively characterized as CmO4, with curium in the extremely rare +8 state; but new experiments seem to indicate that CmO4 does not exist, and have cast doubt on the existence of PuO4 as well.

Halides
The colorless curium(III) fluoride (CmF3) can be made by adding fluoride ions into curium(III)-containing solutions. The brown tetravalent curium(IV) fluoride (CmF4) on the other hand is only obtained by reacting curium(III) fluoride with molecular fluorine:
 * $$\mathrm{2\ CmF_3\ +\ F_2\ \longrightarrow\ 2\ CmF_4}$$

A series of ternary fluorides are known of the form A7Cm6F31 (A = alkali metal).

The colorless curium(III) chloride (CmCl3) is made by reacting curium hydroxide (Cm(OH)3) with anhydrous hydrogen chloride gas. It can be further turned into other halides such as curium(III) bromide (colorless to light green) and curium(III) iodide (colorless), by reacting it with the ammonia salt of the corresponding halide at temperatures of ~400–450 °C:
 * $$\mathrm{CmCl_3\ +\ 3\ NH_4I\ \longrightarrow \ CmI_3\ +\ 3\ NH_4Cl}$$

Or, one can heat curium oxide to ~600°C with the corresponding acid (such as hydrobromic for curium bromide). Vapor phase hydrolysis of curium(III) chloride gives curium oxychloride:
 * $$\mathrm{CmCl_3\ +\ \ H_2O\ \longrightarrow \ CmOCl\ +\ 2\ HCl}$$

Chalcogenides and pnictides
Sulfides, selenides and tellurides of curium have been obtained by treating curium with gaseous sulfur, selenium or tellurium in vacuum at elevated temperature. Curium pnictides of the type CmX are known for nitrogen, phosphorus, arsenic and antimony. They can be prepared by reacting either curium(III) hydride (CmH3) or metallic curium with these elements at elevated temperature.

Organocurium compounds and biological aspects
Organometallic complexes analogous to uranocene are known also for other actinides, such as thorium, protactinium, neptunium, plutonium and americium. Molecular orbital theory predicts a stable "curocene" complex (η8-C8H8)2Cm, but it has not been reported experimentally yet.

Formation of the complexes of the type (BTP = 2,6-di(1,2,4-triazin-3-yl)pyridine), in solutions containing n-C3H7-BTP and Cm3+ ions has been confirmed by EXAFS. Some of these BTP-type complexes selectively interact with curium and thus are useful for separating it from lanthanides and another actinides. Dissolved Cm3+ ions bind with many organic compounds, such as hydroxamic acid, urea, fluorescein and adenosine triphosphate. Many of these compounds are related to biological activity of various microorganisms. The resulting complexes show strong yellow-orange emission under UV light excitation, which is convenient not only for their detection, but also for studying interactions between the Cm3+ ion and the ligands via changes in the half-life (of the order ~0.1 ms) and spectrum of the fluorescence.

Curium has no biological significance. There are a few reports on biosorption of Cm3+ by bacteria and archaea, but no evidence for incorporation of curium into them.

Radionuclides
Curium is one of the most radioactive isolable elements. Its two most common isotopes 242Cm and 244Cm are strong alpha emitters (energy 6 MeV); they have fairly short half-lives, 162.8 days and 18.1 years, and give as much as 120 W/g and 3 W/g of heat, respectively. Therefore, curium can be used in its common oxide form in radioisotope thermoelectric generators like those in spacecraft. This application has been studied for the 244Cm isotope, while 242Cm was abandoned due to its prohibitive price, around 2000 USD/g. 243Cm with a ~30-year half-life and good energy yield of ~1.6 W/g could be a suitable fuel, but it gives significant amounts of harmful gamma and beta rays from radioactive decay products. As an α-emitter, 244Cm needs much less radiation shielding, but it has a high spontaneous fission rate, and thus a lot of neutron and gamma radiation. Compared to a competing thermoelectric generator isotope such as 238Pu, 244Cm emits 500 times more neutrons, and its higher gamma emission requires a shield that is 20 times thicker—2 in of lead for a 1 kW source, compared to 0.1 in for 238Pu. Therefore, this use of curium is currently considered impractical.

A more promising use of 242Cm is for making 238Pu, a better radioisotope for thermoelectric generators such as in heart pacemakers. The alternate routes to 238Pu use the (n,γ) reaction of 237Np, or deuteron bombardment of uranium, though both reactions always produce 236Pu as an undesired by-product since the latter decays to 232U with strong gamma emission. Curium is a common starting material for making higher transuranic and superheavy elements. Thus, bombarding 248Cm with neon (22Ne), magnesium (26Mg), or calcium (48Ca) yields isotopes of seaborgium (265Sg), hassium (269Hs and 270Hs), and livermorium (292Lv, 293Lv, and possibly 294Lv). Californium was discovered when a microgram-sized target of curium-242 was irradiated with 35 MeV alpha particles using the 60 in cyclotron at Berkeley:

Only about 5,000 atoms of californium were produced in this experiment.

The odd-mass curium isotopes 243Cm, 245Cm, and 247Cm are all highly fissile and can release additional energy in a thermal spectrum nuclear reactor. All curium isotopes are fissionable in fast-neutron reactors. This is one of the motives for minor actinide separation and transmutation in the nuclear fuel cycle, helping to reduce the long-term radiotoxicity of used, or spent nuclear fuel.

X-ray spectrometer
The most practical application of 244Cm—though rather limited in total volume—is as α-particle source in alpha particle X-ray spectrometers (APXS). These instruments were installed on the Sojourner, Mars, Mars 96, Mars Exploration Rovers and Philae comet lander, as well as the Mars Science Laboratory to analyze the composition and structure of the rocks on the surface of planet Mars. APXS was also used in the Surveyor 5–7 moon probes but with a 242Cm source.

An elaborate APXS setup has a sensor head containing six curium sources with a total decay rate of several tens of millicuries (roughly one gigabecquerel). The sources are collimated on a sample, and the energy spectra of the alpha particles and protons scattered from the sample are analyzed (proton analysis is done only in some spectrometers). These spectra contain quantitative information on all major elements in the sample except for hydrogen, helium and lithium.

Safety
Due to its radioactivity, curium and its compounds must be handled in appropriate labs under special arrangements. While curium itself mostly emits α-particles which are absorbed by thin layers of common materials, some of its decay products emit significant fractions of beta and gamma rays, which require a more elaborate protection. If consumed, curium is excreted within a few days and only 0.05% is absorbed in the blood. From there, ~45% goes to the liver, 45% to the bones, and the remaining 10% is excreted. In bone, curium accumulates on the inside of the interfaces to the bone marrow and does not significantly redistribute with time; its radiation destroys bone marrow and thus stops red blood cell creation. The biological half-life of curium is about 20 years in the liver and 50 years in the bones. Curium is absorbed in the body much more strongly via inhalation, and the allowed total dose of 244Cm in soluble form is 0.3 μCi. Intravenous injection of 242Cm- and 244Cm-containing solutions to rats increased the incidence of bone tumor, and inhalation promoted lung and liver cancer.

Curium isotopes are inevitably present in spent nuclear fuel (about 20 g/tonne). The isotopes 245Cm–248Cm have decay times of thousands of years and must be removed to neutralize the fuel for disposal. Such a procedure involves several steps, where curium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure, nuclear transmutation, while well documented for other elements, is still being developed for curium.

title: Curium


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Californium

Californium is a synthetic chemical element; it has symbol Cf and atomic number 98. It 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). 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). It was named after the university and the U.S. state of California.

Two crystalline forms exist at normal pressure: one above and one below 900 C. A third form exists at high pressure. Californium slowly tarnishes in air at room temperature. Californium compounds are dominated by the +3 oxidation state. The most stable of californium's twenty known isotopes is californium-251, with a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust. 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.

Californium is one of the few transuranium elements with 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. It 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.

Physical properties
Californium is a silvery-white actinide metal with a melting point of 900 ± and an estimated boiling point of 1743 K. The pure metal is malleable and is easily cut with a razor blade. Californium metal starts to vaporize above 300 C when exposed to a vacuum. Below 51 K 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 it is paramagnetic (external magnetic fields can make it magnetic). It forms alloys with lanthanide metals but little is known about the resulting materials.

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). The α form exists below 600–800 °C with a density of 15.10 g/cm3 and the β form exists above 600–800 °C with a density of 8.74 g/cm3. 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 bulk modulus of a material is a measure of its resistance to uniform pressure. Californium's bulk modulus is $50 GPa$, which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium (70 GPa).

Chemical properties and compounds
Californium exhibits oxidation states of 4, 3, or 2. It typically forms eight or nine bonds to surrounding atoms or ions. 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. Compounds in the +4 oxidation state are strong oxidizing agents and those in the +2 state are strong reducing agents.

The element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added. Californium reacts when heated with hydrogen, nitrogen, or a chalcogen (oxygen family element); reactions with dry hydrogen and aqueous mineral acids are rapid.

Californium is only water-soluble as the californium(III) cation. Attempts to reduce or oxidize the +3 ion in solution have failed. The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate, or hydroxide. Californium is the heaviest actinide to exhibit covalent properties, as is observed in the californium borate.

Isotopes
Twenty isotopes of californium are known (mass number ranging from 237 to 256 ); the most stable are $2$Cf with half-life 898 years, $2$Cf with half-life 351 years, $2$Cf at 13.08 years, and $3$Cf at 2.645 years. All other isotopes have half-life shorter than a year, and most of these have half-lives less than 20 minutes.

$3$Cf is formed by beta decay of berkelium-249, and most other californium isotopes are made by subjecting berkelium to intense neutron radiation in a nuclear reactor. Though californium-251 has the longest half-life, its production yield is only 10% due to its tendency to collect neutrons (high neutron capture) and its tendency to interact with other particles (high neutron cross section).

$3$Cf is a very strong neutron emitter, which makes it extremely radioactive and harmful. $3$Cf, 96.9% of the time, alpha decays to curium-248; the other 3.1% of decays are spontaneous fission. One microgram (μg) of $3$Cf emits 2.3 million neutrons per second, an average of 3.7 neutrons per spontaneous fission. Most other isotopes of californium, alpha decay to curium (atomic number 96).

History
Californium was first made at University of California Radiation Laboratory, Berkeley, by physics researchers Stanley Gerald Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg, about February 9, 1950. It was the sixth transuranium element to be discovered; the team announced its discovery on March 17, 1950.

To produce californium, a microgram-size target of curium-242 was bombarded with 35 MeV alpha particles  in the 60 in cyclotron at Berkeley, which produced californium-245  plus one free neutron.

To identify and separate out the element, ion exchange and adsorsion methods were undertaken. Only about 5,000 atoms of californium were produced in this experiment, and these atoms had a half-life of 44 minutes.

The discoverers named the new element after the university and the state. This was a break from the convention used for elements 95 to 97, which drew inspiration from how the elements directly above them in the periodic table were named. However, the element directly above element 98 in the periodic table, dysprosium, has a name that means "hard to get at", so the researchers decided to set aside the informal naming convention. They added that "the best we can do is to point out [that] ... searchers a century ago found it difficult to get to California".

Weighable amounts of californium were first produced by the irradiation of plutonium targets at Materials Testing Reactor at National Reactor Testing Station, eastern Idaho; these findings were reported in 1954. The high spontaneous fission rate of californium-252 was observed in these samples. The first experiment with californium in concentrated form occurred in 1958. The isotopes $6$Cf to $8$Cf were isolated that same year from a sample of plutonium-239 that had been irradiated with neutrons in a nuclear reactor for five years. Two years later, in 1960, Burris Cunningham and James Wallman of Lawrence Radiation Laboratory of the University of California created the first californium compounds—californium trichloride, californium(III) oxychloride, and californium oxide—by treating californium with steam and hydrochloric acid.

The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, started producing small batches of californium in the 1960s. By 1995, HFIR nominally produced 500 mg of californium annually. Plutonium supplied by the United Kingdom to the United States under the 1958 US–UK Mutual Defence Agreement was used for making californium.

The Atomic Energy Commission sold $5$Cf to industrial and academic customers in the early 1970s for $10 per microgram, and an average of 150 mg of $2$Cf were shipped each year from 1970 to 1990. Californium metal was first prepared in 1974 by Haire and Baybarz, who reduced californium(III) oxide with lanthanum metal to obtain microgram amounts of sub-micrometer thick films.

Occurrence
Traces of californium can be found near facilities that use the element in mineral prospecting and in medical treatments. The element is fairly insoluble in water, but it adheres well to ordinary soil; and concentrations of it in the soil can be 500 times higher than in the water surrounding the soil particles.

Nuclear fallout from atmospheric nuclear weapons testing prior to 1980 contributed a small amount of californium to the environment. Californium-249, -252, -253, and -254 have been observed in the radioactive dust collected from the air after a nuclear explosion. Californium is not a major radionuclide at United States Department of Energy legacy sites since it was not produced in large quantities.

Californium was once believed to be produced in supernovas, as their decay matches the 60-day half-life of $4$Cf. However, subsequent studies failed to demonstrate any californium spectra, and supernova light curves are now thought to follow the decay of nickel-56.

The transuranic elements americium to fermium, including californium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so.

Spectral lines of californium, along with those of several other non-primordial elements, were detected in Przybylski's Star in 2008.

Production
Californium is produced in nuclear reactors and particle accelerators. Californium-250 is made by bombarding berkelium-249 ($251$Bk) with neutrons, forming berkelium-250 ($249$Bk) via neutron capture (n,γ) which, in turn, quickly beta decays (β$250$) to californium-250 ($252$Cf) in the following reaction:
 * (n,γ) → + β$249$

Bombardment of $252$Cf with neutrons produces $252$Cf and $252$Cf.

Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of $1 0$Cf and microgram amounts of $249$Cf. As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce mainly californium-252 with lesser amounts of isotopes 249 to 255.

Microgram quantities of $252$Cf are available for commercial use through the U.S. Nuclear Regulatory Commission. Only two sites produce $252$Cf: Oak Ridge National Laboratory in the U.S., and the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. As of 2003, the two sites produce 0.25 grams and 0.025 grams of $252$Cf per year, respectively.

Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. $2$Cf is at the end of a production chain that starts with uranium-238, and includes several isotopes of plutonium, americium, curium, and berkelium, and the californium isotopes 249 to 253 (see diagram).

Applications

Californium-252 has a number of specialized uses as a strong neutron emitter; it produces 139 million neutrons per microgram per minute. This property makes it useful as a startup neutron source for some nuclear reactors and as a portable (non-reactor based) neutron source for neutron activation analysis to detect trace amounts of elements in samples. Neutrons from californium are used as a treatment of certain cervical and brain cancers where other radiation therapy is ineffective. It has been used in educational applications since 1969 when Georgia Institute of Technology got a loan of 119 μg of 252Cf from the Savannah River Site. It is also used with online elemental coal analyzers and bulk material analyzers in the coal and cement industries.

Neutron penetration into materials makes californium useful in detection instruments such as fuel rod scanners; neutron radiography of aircraft and weapons components to detect corrosion, bad welds, cracks and trapped moisture; and in portable metal detectors. Neutron moisture gauges use 252Cf to find water and petroleum layers in oil wells, as a portable neutron source for gold and silver prospecting for on-the-spot analysis, and to detect ground water movement. The main uses of 252Cf in 1982 were, reactor start-up (48.3%), fuel rod scanning (25.3%), and activation analysis (19.4%). By 1994, most 252Cf was used in neutron radiography (77.4%), with fuel rod scanning (12.1%) and reactor start-up (6.9%) as important but secondary uses. In 2021, fast neutrons from 252Cf were used for wireless data transmission.

251Cf has a very small calculated critical mass of about 5 kg, high lethality, and a relatively short period of toxic environmental irradiation. The low critical mass of californium led to some exaggerated claims about possible uses for the element.

In October 2006, researchers announced that three atoms of oganesson (element 118) had been identified at Joint Institute for Nuclear Research in Dubna, Russia, from bombarding 249Cf with calcium-48, making it the heaviest element ever made. The target contained about 10 mg of 249Cf deposited on a titanium foil of 32 cm2 area. Californium has also been used to produce other transuranium elements; for example, lawrencium was first synthesized in 1961 by bombarding californium with boron nuclei.

Precautions
Californium that bioaccumulates in skeletal tissue releases radiation that disrupts the body's ability to form red blood cells. The element plays no natural biological role in any organism due to its intense radioactivity and low concentration in the environment.

Californium can enter the body from ingesting contaminated food or drinks or by breathing air with suspended particles of the element. Once in the body, only 0.05% of the californium will reach the bloodstream. About 65% of that californium will be deposited in the skeleton, 25% in the liver, and the rest in other organs, or excreted, mainly in urine. Half of the californium deposited in the skeleton and liver are gone in 50 and 20 years, respectively. Californium in the skeleton adheres to bone surfaces before slowly migrating throughout the bone.

The element is most dangerous if taken into the body. In addition, californium-249 and californium-251 can cause tissue damage externally, through gamma ray emission. Ionizing radiation emitted by californium on bone and in the liver can cause cancer.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Californium


text:
Christian Social Union in Bavaria

The Christian Social Union in Bavaria (German:, CSU) is a Christian democratic and conservative   political party in Germany. Having a regionalist identity, the CSU operates only in Bavaria while its larger counterpart, the Christian Democratic Union (CDU), operates in the other fifteen states of Germany. It differs from the CDU by being somewhat more conservative in social matters, following Catholic social teaching. The CSU is considered the de facto successor of the Weimar-era Catholic Bavarian People's Party.

At the federal level, the CSU forms a common faction in the Bundestag with the CDU which is frequently referred to as the Union Faction (die Unionsfraktion) or simply CDU/CSU. The CSU has 43 seats in the Bundestag since the 2021 federal election, making it currently the second smallest of the seven parties represented. The CSU is a member of the European People's Party and the International Democracy Union.

Party leader Markus Söder serves as Minister-President of Bavaria, a position that CSU representatives have held from 1946 to 1954 and again since 1957. From 1962 to 2008 and from 2013 to 2018, the CSU had the absolute majority in the Bavarian Landtag.

History

Franz Josef Strauß (1915–1988) had left behind the strongest legacy as a leader of the party, having led the party from 1961 until his death in 1988. His political career in the federal cabinet was unique in that he had served in four ministerial posts in the years between 1953 and 1969. From 1978 until his death in 1988, Strauß served as the Minister-President of Bavaria. Strauß was the first leader of the CSU to be a candidate for the German chancellery in 1980. In the 1980 federal election, Strauß ran against the incumbent Helmut Schmidt of the Social Democratic Party of Germany (SPD) but lost thereafter as the SPD and the Free Democratic Party (FDP) managed to secure an absolute majority together, forming a social-liberal coalition.

The CSU has led the Bavarian state government since it came into existence in 1946, save from 1954 to 1957 when the SPD formed a state government in coalition with the Bavaria Party and the state branches of the GB/BHE and FDP.

Initially, the separatist Bavaria Party (BP) successfully competed for the same electorate as the CSU, as both parties saw and presented themselves as successors to the BVP. The CSU was ultimately able to win this power struggle for itself. Among other things, the BP was involved in the "casino affair" under dubious circumstances by the CSU at the end of the 1950s and lost considerable prestige and votes. In the 1966 state election, the BP finally left the state parliament.

Before the 2008 elections in Bavaria, the CSU perennially achieved absolute majorities at the state level by itself. This level of dominance is unique among Germany's 16 states. Edmund Stoiber took over the CSU leadership in 1999. He ran for Chancellor of Germany in 2002, but his preferred CDU/CSU–FDP coalition lost against the SPD candidate Gerhard Schröder's SPD–Green alliance.

In the 2003 Bavarian state election, the CSU won 60.7% of the vote and 124 of 180 seats in the state parliament. This was the first time any party had won a two-thirds majority in a German state parliament. The Economist later suggested that this exceptional result was due to a backlash against Schröder's government in Berlin. The CSU's popularity declined in subsequent years. Stoiber stepped down from the posts of Minister-President and CSU chairman in September 2007. A year later, the CSU lost its majority in the 2008 Bavarian state election, with its vote share dropping from 60.7% to 43.4%. The CSU remained in power by forming a coalition with the FDP. In the 2009 general election, the CSU received only 42.5% of the vote in Bavaria in the 2009 election, which by then constituted its weakest showing in the party's history.

The CSU made gains in the 2013 Bavarian state election and the 2013 federal election, which were held a week apart in September 2013. The CSU regained their majority in the Bavarian Landtag and remained in government in Berlin. They had three ministers in the Fourth Merkel cabinet, namely Horst Seehofer (Minister of the Interior, Building and Community), Andreas Scheuer (Minister of Transport and Digital Infrastructure) and Gerd Müller (Minister for Economic Cooperation and Development).

The 2018 Bavarian state election yielded the worst result for the CSU in the state elections (top candidate Markus Söder) since 1950 with 37.2% of votes, a decline of over ten percentage points compared to the last result in 2013. After that, the CSU had to form a new coalition government with the minor partner Free Voters of Bavaria.

The 2021 German federal election saw the worst election result ever for the Union. The CSU also had a weak showing with 5.2% of votes nationally and 31.7% of the total in Bavaria.

Relationship with the CDU
The CSU is the sister party of the Christian Democratic Union (CDU). Together, they are called the Union. The CSU operates only within Bavaria, and the CDU operates in all states other than Bavaria. While virtually independent, at the federal level the parties form a common CDU/CSU faction. No Chancellor has ever come from the CSU, although Strauß and Edmund Stoiber were CDU/CSU candidates for Chancellor in the 1980 federal election and the 2002 federal election, respectively, which were both won by the Social Democratic Party of Germany (SPD). Below the federal level, the parties are entirely independent.

Since its formation, the CSU has been more conservative than the CDU. CSU and the state of Bavaria decided not to sign the Grundgesetz of the Federal Republic of Germany as they could not agree with the division of Germany into two states after World War II. Although Bavaria like all German states has a separate police and justice system (distinctive and non-federal), the CSU has actively participated in all political affairs of the German Parliament, the German government, the German Bundesrat, the parliamentary elections of the German President, the European Parliament and meetings with Mikhail Gorbachev in Russia.

Like the CDU, the CSU is pro-European, although some Eurosceptic tendencies were shown in the past.

Ministers-president
The CSU has contributed eleven of the twelve Ministers-President of Bavaria since 1945, with only Wilhelm Hoegner (1945–1946, 1954–1957) of the SPD also holding the office.

title: Christian Social Union in Bavaria


text:
Corporate title

Corporate titles or business titles are given to corporate officers to show what duties and responsibilities they have in the organization. Such titles are used by publicly and privately held for-profit corporations, cooperatives, non-profit organizations, educational institutions, partnerships, and sole proprietorships that also confer corporate titles.

Variations
There are considerable variations in the composition and responsibilities of corporate titles.

Within the corporate office or corporate center of a corporation, some corporations have a chairman and chief executive officer (CEO) as the top-ranking executive, while the number two is the president and chief operating officer (COO); other corporations have a president and CEO but no official deputy. Typically, senior managers are "higher" than vice presidents, although many times a senior officer may also hold a vice president title, such as executive vice president and chief financial officer (CFO). The board of directors is technically not part of management itself, although its chairman may be considered part of the corporate office if he or she is an executive chairman.

A corporation often consists of different businesses, whose senior executives report directly to the CEO or COO, but that depends on the form of the business. If organized as a division then the top manager is often known as an executive vice president (EVP). If that business is a subsidiary which has considerably more independence, then the title might be chairman and CEO.

In many countries, particularly in Europe and Asia, there is a separate executive board for day-to-day business and supervisory board (elected by shareholders) for control purposes. In these countries, the CEO presides over the executive board and the chairman presides over the supervisory board, and these two roles will always be held by different people. This ensures a distinction between management by the executive board and governance by the supervisory board. This seemingly allows for clear lines of authority. There is a strong parallel here with the structure of government, which tends to separate the political cabinet from the management civil service.

In the United States and other countries that follow a single-board corporate structure, the board of directors (elected by the shareholders) is often equivalent to the European or Asian supervisory board, while the functions of the executive board may be vested either in the board of directors or in a separate committee, which may be called an operating committee (J.P. Morgan Chase), management committee (Goldman Sachs), executive committee (Lehman Brothers), executive council (Hewlett-Packard), or executive board (HeiG) composed of the division/subsidiary heads and senior officers that report directly to the CEO.

United States
State laws in the United States traditionally required certain positions to be created within every corporation, such as president, secretary and treasurer. Today, the approach under the Model Business Corporation Act, which is employed in many states, is to grant corporations discretion in determining which titles to have, with the only mandated organ being the board of directors.

Some states that do not employ the MBCA continue to require that certain offices be established. Under the law of Delaware, where most large US corporations are established, stock certificates must be signed by two officers with titles specified by law (e.g. a president and secretary or a president and treasurer). Every corporation incorporated in California must have a chairman of the board or a president (or both), as well as a secretary and a chief financial officer.

Limited liability company (LLC)-structured companies are generally run directly by their members, but the members can agree to appoint officers such as a CEO or to appoint "managers" to operate the company.

American companies are generally led by a CEO. In some companies, the CEO also has the title of "president". In other companies, a president is a different person, and the primary duties of the two positions are defined in the company's bylaws (or the laws of the governing legal jurisdiction). Many companies also have a CFO, a chief operating officer (COO) and other senior positions such as chief legal officer (CLO), chief strategy officer (CSO), chief marketing officer (CMO), etc. that report to the president and CEO. The next level, which are not executive positions, is middle management and may be called "vice presidents", "directors" or "managers", depending on the size and required managerial depth of the company.

United Kingdom
In British English, the title of managing director is generally synonymous with that of chief executive officer. Managing directors do not have any particular authority under the Companies Act in the UK, but do have implied authority based on the general understanding of what their position entails, as well as any authority expressly delegated by the board of directors.

Japan and South Korea
In Japan, corporate titles are roughly standardized across companies and organizations; although there is variation from company to company, corporate titles within a company are always consistent, and the large companies in Japan generally follow the same outline. These titles are the formal titles that are used on business cards. Korean corporate titles are similar to those of Japan.

Legally, Japanese and Korean companies are only required to have a board of directors with at least one representative director. In Japanese, a company director is called a torishimariyaku (取締役) and a representative director is called a daihyō torishimariyaku (代表取締役). The equivalent Korean titles are isa (이사, 理事) and daepyo-isa (대표이사, 代表理事). These titles are often combined with lower titles, e.g. senmu torishimariyaku or jōmu torishimariyaku for Japanese executives who are also board members. Most Japanese companies also have statutory auditors, who operate alongside the board of directors in supervisory roles.

Under the commercial code in Japan, Jugyōin (従業員) meaning the "employee", is different from Kaishain (会社員), meaning the "stockholders".

The typical structure of executive titles in large companies includes the following: The top management group, comprising jomu/sangmu and above, is often referred to collectively as "cadre" or "senior management" (幹部 or 重役; kambu or juyaku in Japanese; ganbu or jungyŏk in Korean).

Some Japanese and Korean companies have also adopted American-style titles, but these are not yet widespread and their usage varies. For example, although there is a Korean translation for "chief operating officer" (최고운영책임자, choego unyŏng chaegimja), not many companies have yet adopted it with the exception of a few multi-national companies such as Samsung and CJ (a spin-off from Samsung), while the CFO title is often used alongside other titles such as bu-sajang (SEVP) or Jŏnmu (EVP).

Since the late 1990s, many Japanese companies have introduced the title of shikkō yakuin (執行役員) or 'officer', seeking to emulate the separation of directors and officers found in American companies. In 2002, the statutory title of shikkō yaku (執行役) was introduced for use in companies that introduced a three-committee structure in their board of directors. The titles are frequently given to buchō and higher-level personnel. Although the two titles are very similar in intent and usage, there are several legal distinctions: shikkō yaku make their own decisions in the course of performing work delegated to them by the board of directors, and are considered managers of the company rather than employees, with a legal status similar to that of directors. Shikkō yakuin are considered employees of the company that follow the decisions of the board of directors, although in some cases directors may have the shikkō yakuin title as well.

Senior management
The highest-level executives in senior management usually have titles beginning with "chief" and ending with "officer", forming what is often called the "C-suite", or "CxO", where "x" is a variable that could be any functional area (not to be confused with CXO). The traditional three such officers are CEO, COO, and CFO. Depending on the management structure, titles may exist instead of, or be blended/overlapped with, other traditional executive titles, such as president, various designations of vice presidents (e.g. VP of marketing), and general managers or directors of various divisions (such as director of marketing); the latter may or may not imply membership of the board of directors.

Certain other prominent positions have emerged, some of which are sector-specific. For example, chief audit executive (CAE), chief procurement officer (CPO) and chief risk officer (CRO) positions are often found in many types of financial services companies. Technology companies of all sorts now tend to have a chief technology officer (CTO) to manage technology development. A chief information officer (CIO) oversees information technology (IT) matters, either in companies that specialize in IT or in any kind of company that relies on it for supporting infrastructure.

Many companies now also have a chief marketing officer (CMO), particularly mature companies in competitive sectors, where brand management is a high priority. A chief value officer (CVO) is introduced in companies where business processes and organizational entities are focused on the creation and maximization of value. Approximately 50% of the S&P 500 companies have created a chief strategy officer (CSO) in their top management team to lead strategic planning and manage inorganic growth, which provides a long range perspective versus the tactical view of the COO or CFO. This function often replaces a COO on the C-Suite team, in cases where the company wants to focus on growth rather than efficiency and cost containment. A chief administrative officer (CAO) may be found in many large complex organizations that have various departments or divisions. Additionally, many companies now call their top diversity leadership position the chief diversity officer (CDO). However, this and many other nontraditional and lower-ranking titles are not universally recognized as corporate officers, and they tend to be specific to particular organizational cultures or the preferences of employees.

Specific corporate officer positions
Chairman of the board – presiding officer of the corporate board of directors. The chairman influences the board of directors, which in turn elects and removes the officers of a corporation and oversees the human, financial, environmental and technical operations of a corporation.
 * The CEO may also hold the title of "chairman", resulting in an executive chairman. In this case, the board frequently names an independent member of the board as a lead director. The C-suite is normally led by the CEO.
 * Executive chairman – the chairman's post may also exist as an office separate from that of CEO, and it is considered an executive chairman if that titleholder wields influence over company operations, such as Vince McMahon of WWE, Steve Case of AOL Time Warner, and Douglas Flint of HSBC. In particular, the group chairmanship of HSBC is considered the top position of that institution, outranking the chief executive, and is responsible for leading the board and representing the company in meetings with government figures. Prior to the creation of the group management board in 2006, HSBC's chairman essentially held the duties of a chief executive at an equivalent institution, while HSBC's chief executive served as the deputy. After the 2006 reorganization, the management cadre ran the business, while the chairman oversaw the controls of the business through compliance and audit and the direction of the business.
 * Non-executive chairman – also a separate post from the CEO, unlike an executive chairman, a non-executive chairman does not interfere in day-to-day company matters. Across the world, many companies have separated the roles of chairman and CEO, often resulting in a non-executive chairman, saying that this move improves corporate governance.
 * Chief business officer is a corporate senior executive who assumes full management responsibility for the company's deal making, provides leadership and executes a deal strategy that will allow the company to fulfill its scientific/technology mission and build shareholder value, provides managerial guidance to the company's product development staff as needed.
 * Chief of staff is a corporate director level manager who has overall responsibility for the staff activity within the company who often would have responsibility of hiring and firing of the highest level managers and sometimes directors. They can work with and report directly to managing directors and the chief executive officer.
 * Commissioner
 * Financial control officer, FCO or FC, also comptroller or controller – supervises accounting and financial reporting within an organization
 * Director or member of a board of directors – high-level official with a fiduciary responsibility of overseeing the operation of a corporation and elects or removes officers of a corporation; nominally, directors, other than the chairman are usually not considered to be employees of the company per se, although they may receive compensation, often including benefits; in publicly held companies. A board of directors is normally made up of members (directors) who are a mixture of corporate officials who are also management employees of the company (inside directors) and persons who are not employed by the company in any capacity (outside directors or non-executive directors). In privately held companies, the board of directors often only consists of the statutory corporate officials, and in sole proprietorship and partnerships, the board is entirely optional, and if it does exist, only operates in an advisory capacity to the owner or partners. Non-profit corporations' governing board members may be called directors like most for-profit corporations, or an alternative like trustees, governors, etc.
 * Director – a manager of managers within an organization who is often responsible for a major business function and who sometimes reports to a vice president (in some financial services companies the title vice president has a different meaning). Often used with name of a functional area; finance director, director of finance, marketing director, and so on. Not to be confused with a member of the board of directors, who is also referred to as a director. This is a middle management and not an executive level position, unless it is in the banking industry. Alternatively, a manager of managers is often referred to as a "senior manager' or as an "associate vice president", depending upon levels of management, and industry type.
 * President – legally recognized highest "titled" corporate officer, and usually a member of the board of directors. There is much variation; often the CEO also holds the title of president, while in other organizations if there is a separate CEO, the president is then second highest-ranking position. In such a case the president is often the COO and is considered to be more focused upon daily operations compared to the CEO, who is supposed to be the visionary. If the corporate president is not the COO (such as Richard Parsons of Time Warner from 1995 to 2001), then many division heads report directly to the CEO themselves, with the president taking on special assignments from the CEO.
 * Secretary or company secretary – legally recognized "titled" corporate officer who reports to the board of directors and is responsible for keeping the records of the board and the company. This title is often concurrently held by the treasurer in a dual position called secretary-treasurer; both positions may be concurrently held by the CFO. Note, however, that the secretary has a reporting line to the board of directors, regardless of any other reporting lines conferred by concurrent titles.
 * Treasurer – legally recognized corporate officer entrusted with the fiduciary responsibility of caring for company funds. Often this title is held concurrently with that of secretary in a dual role called secretary-treasurer. It can also be held concurrently with the title of CFO or fall under the jurisdiction of one, though the CFO tends to oversee the finance department instead, which deals with accounting and audits, while the treasurer deals directly with company funds. Note, however, that the treasurer has a reporting line to the board of directors, regardless of any other reporting lines conferred by concurrent titles.
 * Superintendent
 * Owner (sometimes proprietor or sole proprietor, for sole proprietorships)
 * Partner – Used in many different ways. This may indicate a co-owner as in a legal partnership or may be used in a general way to refer to a broad class of employees or temporary/contract workers who are often assigned field or customer service work. Associate is often used in a similar way.
 * Vice chair or vice chairman – officer of the board of directors who may stand in for the chairman in his or her absence. However, this type of vice chairman title on its own usually has only an advisory role and not an operational one (such as Ted Turner at Time Warner). An unrelated definition of vice chair describes an executive who is higher ranking or has more seniority than executive vice president. Sometimes, EVPs report to the vice chair, who in turn reports directly to the CEO (so vice chairs in effect constitute an additional layer of management), other vice chairs have more responsibilities but are otherwise on an equal tier with EVPs. Executive vice chairman are usually not on the board of directors. Royal Bank of Canada previously used vice chairs in their inner management circle until 2004 but have since renamed them as group heads.

Middle management

 * Supervisor
 * Foreman
 * General manager or GM
 * Manager
 * Of counsel – A lawyer working on a part-time or temporary basis for a company or law firm.
 * Vice president – Middle or upper manager in a corporation. They often appear in various hierarchical layers such as executive vice president, senior vice president, associate vice president, or assistant vice president, with EVP usually considered the highest and usually reporting to the CEO or president. Many times, corporate officers such as the CFO, COO, CSO, CIO, CTO, secretary, or treasurer will concurrently hold vice president titles, commonly EVP or SVP. Vice presidents in small companies are also referred to as chiefs of a certain division, such as vice president for finance, or vice president for administration. In some financial contexts, the title of vice president is actually subordinate to a director.

title: Corporate title