Electronic configurations carbides

Q The carbide ion, C22, is a constituent of some compounds of electropositive metals, such as in CaC2. Write down the electronic configuration of the carbide ion and determine the bond order. The C-C distance in CaC2 is 119 pm. Is this distance compatible with your value for the bond order ... 

Self-Test 3.10A Deduce the electron configuration and bond order ot the carbide ion (C22-). 

Calcium carbide (CaC2) is an intermediate in the manufacturing of acetylene (C2IT2). It is the calcium salt of the carbide (also called acetylide) ion (C2 ). What is the electron configuration of this molecular ion What is its bond order ... 

The group 4A elements possess the outer-shell electron configuration ns np. The electronegativities of the elements are generally low (V TABLE 22.8) carbides that formally contain C ions are observed only in the case of a few compounds of carbon with ver)y active metals. Formation of 4-1- ions by electron loss is not observed for any of these elements the ionization energies are too high. The +2 oxidation state is found in the... 

Carbides, like all materials, have a well-defined internal electronic structure which governs their behavior and controls their properties. This means that, in order to understand their mechanism of formation and their general characteristics and properties, it is essential to have a clear picture of the electronic configuration of their constituents. The element common to all carbides is, of course, carbon a short review of its structure follows.Pl... 

The electronic structure of the carbon atom in its ground state is s22s22p2, with the two 2p electrons unpaired, following Hund s rule. In order to account for the normal four-covalence of carbon, we must consider that it is promoted to a valence state based on the configuration 2s2px2py2pz. The ion C4+ does not arise in any normal chemical process the C4 ion may possibly exist in some carbides. In general, however, carbon forms covalent bonds. 

The MO model of C2 predicts a doubly bonded molecule, with all electrons paired, but with both highest occupied molecular orhitals (HOMOs) having tt symmetry. C2 is unusual because it has two tt bonds and no cr bond. Although C2 is a rarely encountered allotrope of carbon (carbon is significantly more stable as diamond, graphite, fullerenes and other polyatomic forms described in Chapter 8), the acetylide ion, C2 , is well known, particularly in compounds with alkali metals, alkaline earths, and lanthanides. According to the molecular orbital model, 2 should have a bond order of 3 (configuration TT TT a-g ). This is supported by the similar C—C distances in acetylene and calcium carbide (acetylide) . ... 

A possible open five-atom cliister is the square pyramid. A square pyramidal cluster of five iron atoms is found in the black carbide Fe5(CO)i5C, which is obtained in trace quantities (0.5% yield) as a minor by-product in the reaction of Fe3(CO)i2 with pentyne at 90°C (41). X-Ray crystallography on Fe5(CO)i5C indicates structure 109, with the five iron atoms at the vertices of a square pyramid whose edges range from 2.59 to 2.67 A. The isolated carbon atom in Fe5(CO)i5C (109) apparently holds open the square face of the square pyramid so that the system of five iron atoms does not collapse into a trigonal bipyramid. Each iron atom in Fe5(CO)i5C (109) has the favored 18-electron rare gas configuration if the isolated carbon atom is regarded as forming four coplanar bonds—a... 

Nitric Oxide. NO is a very active molecule because it has one electron in its relatively low lying LUMO orbital. As a result, it dissociates more readily than CO and it can more easily adopt tilted configurations. Thus, NO dissociates almost completely over a molybdenum carbide film like over pure molybdenum and ruthenium (78). The vibration spectra of NO on the M02C film showed two bands at 1800 and 1761 cm due to the on-top adsorption on two distinct Mo sites. The chemisorption bond between NO and M02C was a strong one since NO remained on the surface to 450 K. 

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