Melting oxidation state

In contrast, when small alkali ions such as lithium are introduced in the melt, oxidation state II becomes stable and disproportionation reactions appear giving rise to a colloidal precipitate together with titanium deposition. As for other refractory metals, the stability range of titanium (II) is greatly enlarged in alkali chloroaluminates. This effect is due to the... 

Apart from TiO and the lower halides already mentioned, the chemistry of these metals in oxidation states lower than 3 is not well established. Addition compounds of the type [TiCl2L2] can be formed with difficulty with ligands such as dimethylformamide and acetonitrile, but their magnetic properties suggest that they also are polymeric with appreciable metal-metal bonding. However, the electronic spectra of Ti in TiCl2/AlCl3 melts and also of Ti incorporated in NaCl crystals (prepared by... 

Investigations of the chemical properties of plutonium have continued in many laboratories throughout the world as it has become available. This has led to the situation where the chemistry of this relative newcomer is as well understood as is that of most of the well-studied elements. The four oxidation states of plutonium—III, IV, V, and VI—lead to a chemistry which is as complex as that of any other element. It is unique among the elements in that these four oxidation states can all exist simultaneously in aqueous solution at appreciable concentration. As a metal, also, its properties are unique. Metallic plutonium has six allotropic forms, in the temperature range from room temperature to its melting point (640 C), and some of these have properties not found in any other known metal. 

Atomic number = 14 atomic weight = 28.09 Melting point = 1410 C boiling point = 2355 °C Density = 2.33 g/cm oxidation state = -4 +4 Electron configuration = Is22s22p23s23p2. 

Z Electronic Configuration Oxidation States Geochemical Properties Ionization Potential (kJ/mol) Melting point (K)... 

A detailed study of the mechanism of the insertion reaction of monomer between the metal-carbon bond requires quantitative information on the kinetics of the process. For this information to be meaningful, studies should be carried out on a homogeneous system. Whereas olefins and compounds such as Zr(benzyl)4 and Cr(2-Me-allyl)3, etc. are very soluble in hydrocarbon solvents, the polymers formed are crystalline and therefore insoluble below the melting temperature of the polyolefine formed. It is therefore not possible to use olefins for kinetic studies. Two completely homogeneous systems have been identified that can be used to study the polymerization quantitatively. These are the polymerization of styrene by Zr(benzyl)4 in toluene (16, 25) and the polymerization of methyl methacrylate by Cr(allyl)3 and Cr(2-Me-allyl)3 (12)- The latter system is unusual since esters normally react with transition metal allyl compounds (10) but a-methyl esters such as methyl methacrylate do not (p. 270) and the only product of reaction is polymethylmethacrylate. Also it has been shown with both systems that polymerization occurs without a change in the oxidation state of the metal. 

Chromium in the crystalline form is a steel-gray, lustrous, hard metal characterized by an atomic weight of 51.996, an atomic number of 24, a density of 7.14 g/cm3, a melting point of 1857°C, and a boiling point of 2672 C. Four chromium isotopes occur naturally Cr-50 (4.3%), -52 (83.8%), -53 (9.6%), and -54 (2.4%), and seven are man-made. Elemental chromium is very stable but is not usually found pure in nature. Chromium can exist in oxidation states ranging from -2 to +6, but is most frequently found in the environment in the trivalent (+3) and hexavalent (+6) oxidation states. The +3 and +6 forms are the most important because the +2, +4, and +5 forms are unstable and are rapidly converted to +3, which in turn is oxidized to +6 (Towill et al. 1978 Langard and Norseth 1979 Ecological Analysts 1981 USPHS 1993). 

In the metallic state, lithium is a very soft metal with a density of 0.534 g/cm. When a small piece is placed on water, it will float as it reacts with the water, releasing hydrogen gas. Lithium s melting point is 179°C, and it has about the same heat capacity as water, with a boiling point of 1,342°C. It is electropositive with an oxidation state of + 1, and it is an excellent conductor of heat and electricity. Its atom is the smallest of the alkali earth metals and thus is the least reactive because its valence electron is in the K shell, which is held closest to its nuclei. 

Sodium is a soft, wax-like silver metal that oxidizes in air. Its density is 0.9674 g/cm, and therefore it floats on water as it reacts with the water releasing hydrogen. It has a rather low melting point (97.6°C) and a boiling point of 883°C. Sodium is an excellent conductor of heat and electricity. It looks much like aluminum but is much softer and can be cut with a knife like butter. Its oxidation state is +1. 

Rubidium is a silvery-white lightweight sohd at room temperature, but it melts at just 38.89°C (102°F), which is just over the human body s normal temperature. Its boiling point is 686°C, its density is 1.532 g/cm, and it has an oxidation state of + 1. 

Not a great deal is known about francium s properties, but some measurements of its most stable isotope have been made. Its melting point is 27°C and its boiling point is 677°C, but its density is unknown. It is assumed to have a +1 oxidation state (similar to all the other alkali metals)... 

Vanadium is a silvery whitish-gray metal that is somewhat heavier than aluminum, but lighter than iron. It is ductile and can be worked into various shapes. It is like other transition metals in the way that some electrons from the next-to-outermost shell can bond with other elements. Vanadium forms many complicated compounds as a result of variable valences. This attribute is responsible for the four oxidation states of its ions that enable it to combine with most nonmetals and to at times even act as a nonmetal. Vanadiums melting point is 1890°C, its boiling point is 3380°C, and its density is 6.11 glam . 

The oxidation state of +8 for ruthenium and its mate osmium is the highest oxidation state of all elements in the transition series. Ruthenium s melting point is 2,310°C, its boiling point is 3,900°C, and its density is 12.45 glcvnr . 

Dubnium s (Unp) most stable isotope, Db-268, is unstable with a half-life of 16 houts. It can change into lawtencium-254 by alpha decay ot into tuthetfotdium-268 by electton cap-tute. Both of these teactions occut thtough a series of decay processes and spontaneous fission (SF). Since so few atoms of unnilpentium (dubnium) are produced, and they have such a short half-life, its melting point, boiling point, and density cannot be determined. In addition, its valence and oxidation state are also unknown. 

As with Uuqs valence and oxidation state, its melting point, boiling point, and density are not known... 

Oxygen fugacity fo directly affects the redox states of trace elements in melts (see, for instance, equation 10.45). Figure 10.12 shows the effects of fo on the oxidation state of Ti and V in an Na2Si205 melt at T = 1085 °C, according to the... 

Figure 10,12 Effects of oxygen fugacity on oxidation state of Ti and V in Na2Si205 melt at r = 1085 °C (experimental data from Johnston, 1964, 1965, and Johnston and Chelko, 1966).

Tricyclopentadienide complexes of many of the actinides are known (Ac = Th, U, Pu, Am, Cm, Bk, Cf). Indeed, these are the only cyclopentadienide complexes known for the transplutonium elements, where -(-3 is the most stable oxidation state. The transplutonium elements were all prepared by a microchemical procedure which utilized a melt of biscyclopentadienyl beryllium (6) according to ... 

Hard blue-white metal body-centered cubic crystal density 7.19 g/cm melts at 1,875°C vaporizes at 2,199°C electrical resistivity at 20°C, 12.9 microhm-cm magnetic susceptibility at 20°C, 3.6x10 emu standard electrode potential 0.71 V (oxidation state 0 to -i-3). 

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