Bismuth ionic compounds

The radius of the second cation in known MuNbOFs, MU2Nb03F3 and Mul2Nb05F compounds containing bi- and trivalent metals, is usually similar to that of niobium s ionic radius. Such compounds cannot be considered as having an island-type structure and will be discussed later on. Only bismuth-containing compounds (Bi3+) display the presence of different cationic sublattices in their crystal structure. 

Table 13.2 shows some of the properties of the trihalides of the Group VA elements. Several trends in the data shown in Table 13.2 are of interest. For example, the trihalides of phosphorus and arsenic can be considered as covalent molecules. As a result, the intermolecular forces are dipole-dipole and London forces that are weak. Therefore, the melting and boiling points increase with molecular weight as expected. The trifluorides of antimony and bismuth are essentially ionic compounds and the melting points are much higher than those of the halogen derivatives that are more covalent. 

There are some important exceptions to the rules discussed here. For example, tin forms both Sn2+ and Sn4+ ions, and lead forms both Pb2+ and Pb4+ ions. Also, bismuth forms Bi3+ and Bi5+ ions, and thallium forms Tl+ and Tl3+ ions. There are no simple explanations for the behavior of these ions. For now, just note them as exceptions to the very useful rule that ions generally adopt noble gas electron configurations in ionic compounds. Our discussion here refers to representative metals. The transition metals exhibit more complicated behavior, forming a variety of ions that will be considered in Chapter 20. 

Bismuth ore, often called bismuth glance, contains an ionic compound consisting of the elements bismuth and sulfur. A sample of the pure compound is found to contain 32.516 g Bi and 7.484 g S. What is the empirical formula for this compound What is its name ... 

Bismuth is the most diamagnetic of all metals and has low thermal conductivity. Since bismuth expands upon solidification, it is used to make castings for objects subjected to high temperatures. It is used as a replacement for lead in solders, shot for hunting, fishing sinkers, ceramic glazes, and brasses for plumbing applications. It is also used as a carrier for (an isotope of uranium) fuel in atomic reactors. Ionic compounds of bismuth are used in cosmetics and medicine. 

Bismuth and antimony tend to be metallic, readily losing electrons to form cations. Although these elements have five valence electrons, so much energy is required to remove all five that no ionic compounds containing Bi or Sb ions are known. 

Antimony and bismuth tend to be metallic, although no ionic compounds containing Sb and Bi are known the compounds containing Sb(V) and Bi(V) are molecular rather than ionic... 

Ionic compounds are usually scarcely soluble, but covalent compounds such as hydrogen halides and many organic compounds are soluble. Examples are hydrocarbons, carboxylic acids, acid chlorides, nitriles, aldehydes, ketones, alcohols, amines and nitrocompounds, but the conductivities of their solutions are very small. Many acceptor halides such as those of aluminium, titanium(IV), tin(IV), phosphorus(V), arsenic(III) and bismuth(III) as well as ferric chloride show reasonable solubilities due to interaction with liquid hydrogen sulphide. Solvates of AICI3, AlBrs, TiCl4, SnCU, BCI3 and others have been described . 

Fig.6.1 depicts the Ebsworth diagram of N and P in acidic solution as well as N in basic solution. The top two elements in this group N and P are typical non-metals. The metallic character, which appears in the heavier elements, increases down the group, although the conductivity of solid Bi is not high. The typical oxidation numbers of all the members of the group are +3 and +5 but the stability of the +3 state in Bi is greater than the +S state (inert pair effect). The chemistry of N and P is dominated by covalent bond formation. On the other hand, ionic compounds of Bi(III) are the common bismuth compounds. The oxides of N and P are acidic in nature (except the neutral N2O and NO), the amphoteric nature becomes apparent in the oxides of the heavier elements. 

The +3 oxidation state is exhibited by bismuth in the vast majority of its compounds. A few inorganic and a variety of organic compounds, however, contain the element in the +5 state. Other rarer oxidation states reported for bismuth include +2, +1, and —3. Bismuth also forms polynuclear ionic species with oxidation states that ate usually fractional and range from —1 to +1. 

Bismuth Trifluoride. Bismuth(III) duoride is a white to grey-white powder, density 8.3 g/mL, that is essentially isomorphous with orthorhombic YF, requiring nine-coordination about the bismuth (11). It has been suggested that BiF is best considered an eight-coordinate stmcture with the deviation from the YF stmcture resulting from stereochemical activity of the bismuth lone-pair electrons. In accord with its stmcture, the compound is the most ionic of the bismuth haUdes. It is almost insoluble in water (5.03 0.05 x 10 M at pH 1.15) and dissolves only to the extent of 0.010 g per 100 g of anhydrous HF at 12.4°C. 

Bismuth Trichloride. Bismuth(III) chloride is a colodess, crystalline, dehquescent soHd made up of pyramidal molecules (19). The nearest intermolecular Bi—Cl distances are 0.3216 nm and 0.3450 nm. The density of the soHd is 4.75 g/mL and that of the Hquid at 254°C is 3.851 g/mL. The vapor density corresponds to that of the monomeric species. The compound is monomeric in dilute ether solutions, but association occurs at concentrations greater than 0.1 Af. The electrical conductivity of molten BiCl is of the same order of magnitude as that found for ionic substances. 

Bismuth Triiodlde. Bismuth(Ill) iodide is a greenish black crystalline powder. The iodines are in a hexagonal close-packed array with each bismuth having six nearest-neighbor iodines at 0.32 nm (21). This suggests that the lone pair on bismuth is stereochemicaHy inactive and that the compound is largely ionic in character. 

The delayed light emission as observed from the Bolonian stone is now classified as phosphorescence. We know now that these stones contain barium sulfate with traces of bismuth and manganese, and that the corresponding reducing process concerns the transformation of sulfate into sulfur. It is now well known that alkaline earth metal sulfates emit phosphorescence that strongly increases when traces of heavy metals are present. The so-called inorganic multi-component compounds phosphor and crystallophosphor are in fact polycrystalline substances containing traces of some ionic activators of luminescence. 

More recently, some other compounds containing polyoxometallates coordinated to Bi were reported by U. Kortz et al., who investigated the interactions of amino acids with polyoxomolybdates in the presence of inter alia Bi +-ions [55,56]. A series of ionic compoimds with anions of the general formula [XM06O21 (amino acid)3] (X = As , Sb , Bi ) were prepared. In case of the bismuth derivatives the amino acids HOOC(CH2) NH2 (n = 1, 2, 3) and L-HOOCCH[(CH2)4NH2]NH2 were reacted with Na2Mo04, Bi203 and KCl in an aqueous medium (Eq. 8). 

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