Bonding semimetals

Vibrational spectra of intra- and inter-metal and semimetal bonds. E. Maslowsky, Chem. Rev., 1971, 71, 507-524 (248). 

Chlorine forms ionic bonds with almost all the metals and molecular bonds with the semimetals and nonmetals. With group 1 metals it produces well-known salts when chlorine s —1 ion combines with this group s +1 ions (e.g, NaCl, LiCl, and KCl). Group 2 metals have +2 ions and thus, when combined with —1 ions of chlorine, form salts such as magnesium chloride (MgCl ), calcium chloride (CaCy, and barium chloride (BaCy. 

The group 3A elements—B, Al, Ga, In, and T1—are metals except for boron, which is a semimetal. Boron is a semiconductor and forms molecular compounds. Boranes, such as diborane (B2H6), are electron-deficient molecules that contain three-center, two-electron bonds (B-H-B). 

Finally, it was a great surprise to discover that tellurium, a typical semimetal, undergoes reactions typical of covalent compounds and that none of the Te-N bonds containing heterocyclic molecules so far prepared tend to explode. 

The semimetals, or metalloids, are known to exhibit some of the properties of metals and some of those of nonmetals. The semimetals are B, Si, Ge, As, Sb, Te, and At. They are highlighted in bold in the partial periodic table in Figure 4.1. The elements located to the left of the semimetals are the metals those to the right of the semimetals are the nonmetals. Identifying an element as a metal, nonmetal, or semimetal is important in identifying periodic trends and in identifying the types of bonds that atoms will form with each other. 

Investigations into nonsynthetic aspects of the Direct Reaction have usually focused on their possible uses to extract metals from solids. The substrate may be a pure metal, a metal alloy, or a compound between a metal and a semimetal. In these applications, the yield may or may not be important. It is not even necessary that the metal-carbon bond be sufficiently stable to isolate the alkylmetals formed even if the initially... 

In all cases the metal ion was monovalent and the compounds contain no Q-Q bonds. In most cases the compounds are valence precise, diamagnetic, narrow bandgap semiconductors or semimetals. 

With their understanding of the nature of the chemical bond and the quantum mechanical model of atoms and molecules, scientists now have an improved understanding of why and how metals, semimetals, and nonmetals differ from each other. The properties of nonmetals are largely determined by the number of valence electrons that nonmetallic... 

In the semimetals antimony, arsenic and bismuth, bonding effects are more pronounced, and the structures are not related to the simple structures of most metals. Bismuth, the heaviest, is the most metallic , and phosphorus, lying above antimony in the periodic table, is not even considered to be a semimetal. 

A weakly acidic behavior is typical of the sdanol groups of silica as well as of the B—OH groups of boria-containing materials. Considering that aluminum is at the border between metal and semimetal character and that aluminum hydroxides are typically amphoteric, both bonding concepts may apply. In other words, the properties of bulk alumina are better explained in terms of ionicity of the Al —bonds, whereas the Al—OH groups at the surface may have a more covalent character. 

These volumes contain theoretical and experimental papers on chemical bonds in crystals, especially those in semiconductors and semimetals. 

Many nonmetals and semimetals have more than one oxidation state, such as nitrogen with oxidation states that range from -3 to +5. Also, the common oxidation states of nonmetals tend to decrease in units of two for example see chlorine +7, +5, +3, +1, -1. This pattern of two is due to a pair of electrons that remain as a pair and yet do not form any bonds (the inert pair effect). 

Associate the regions (A, B, C) with bond types (metallic, covalent, ionic). The "SM" region is sometimes called semimetals. 

For each of the following compounds, place a point on the bond-type triangle. Classify each compound as metallic, covalent, ionic, semimetal. 

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