Bond enthalpies group 16 elements

FIGURE 5. Me3M-R bond dissociation enthalpies (M = element from Group 14 R = H or Me) versus the enthalpies of formation of gaseous M... 

In the chemistry of main-group element sulfoxide complexes, a relationship between Aj/(S=0) and the enthalpy of formation of the sulfoxide complex has been derived (159). The applicability of the equation has only been examined for O-l SO complexes, and the constraints on using Ai (S=0) as a measure of metal-ligand bond strength should be borne in mind during its application. 

This monograph contains enthalpies of formation, heat capacities, entropies, and metal-ligand bond dissociation enthalpies of organometallic compounds of transition and main group elements. 

The relationships between bond enthalpy, bond length and bond order which appear relatively simple in the case of a main group element such as carbon and its compounds, are more difficult to establish when the d-transition metal elements and their compounds are considered. Progress in establishing these relationships for metals is severely hindered by a lack of relevant thermochemical data. This paper reviews some of the more useful information that is available for diatomic molecules, for polynuclear binary carbonyls and for binuclear complexes of the d-transition elements. 

Some general trends in bond enthalpies down a main group can be noted from Table 2.4. In Groups 14, 15, 16 and 17, if the element in the period from Li to F is Aj, the period Na to Cl is A2, etc., then... 

The reasons for the differences can be explained using bond enthalpies. As we have seen, the values of the first ionization energies fall as a group is descended. Bond enthalpies to a particular element also decrease. 

Bond enthalpy terms can be used to explain differences in the reactivity and bond strengths of the main group elements and to explain general trends such as the inert pair effect and the tendency to form double or single bonds. 

Table 13.2 Some experimental covalent bond enthalpy terms (kJmoP ) the values for single bonds refer to the group 14 elements in tetrahedral environments.

Table 13.2 lists some experimentally determined values for covalent bond enthalpy terms. When we try to interpret the chemistry of the group 14 elements on the basis of such bond energies, caution is necessary for two reasons ... 

Analogies between groups 14 and 15 are seen if we consider certain bonding aspects. Table 14.3 lists some covalent bond enthalpy terms for group 15 elements. Data for most single bonds follow trends reminiscent of those in group 14... 

Some bond enthalpy terms for compounds of the group 16 elements are given in Table 15.2. In discussing groups 14 and 15, we emphasized the importance of ( j-p)7r-bonding for the... 

The chemistry exhibited by the first member of a nonmetal group can differ from that of subsequent members. For example, nonmetals in period 3 and below can accommodate a larger number of bonded neighbors. (Section 8.7) Another important difference is that the first element in any group can more readily form tt bonds. This trend is due, in part, to size because small atoms are able to approach each other more closely. As a result, the overlap of p orbitals, which results in the formation of tt bonds, is more effective for the first element in each group (T FIGURE 22.2). More effective overlap means stronger tt bonds, reflected in bond enthalpies. (Section 8.8) For example, the difference between the enthalpies of the C—C bond and the C=C bond is about 270 kj/mol ... 

Which property of the group 6A elements might be the one depicted in the graph shown here (a) electronegativity, (b) first ionization energy, (c) density, (d) X—X single-bond enthalpy, (e) electron affinity Explain your answer. [Sections 22.5 and 22.6]... 

---