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8 Chemical Bonding Solutions to Exercises 8.65 (a) 16 8 e- pairs Be Cl: This structure violates the octet rule; Be has only 4 around it. (b) Be Be Cl: Be Cl: (c) The formal charges on each of the atoms in the four resonance structures are: Be Cl: Be Be Cl: Be 0 0 0 +1 -2 +1 0 -2 +2 +2 -2 0 Formal charges are minimized on the structure that violates the octet rule; this form is probably dominant. 8.66 (a) 26 e⁻, 13 e- pairs +3 +2 +1 0 Xe :-1 -1: Xe -1 0 0 0 Xe 0 : O: : : O: -1 0 -1 0 (b) Yes, the structure with no double bonds obeys the octet rule for all atoms. (c) The structure with one double bond has 3 resonance structures (3 possible positions for the double bond), as does the structure with two double and one single bond (3 possible positions for the single bond). The total number of resonance structures is then 8. (d) The structure with 3 double bonds minimizes formal charges on all atoms. 8.67 13 pairs 0 +1 -1 1- 0 0 0 1- 1- 0 -1 0 H S : H S H S : : -1 -1 0 Three resonance structures for are shown above. Because we are dealing with an ion with a 1- charge, the sum of the formal charges of the atoms will be -1. That is, no correct Lewis structure will have all atoms with zero formal charge. The structure with no double bonds obeys the octet rule for all atoms, but does not lead to minimum formal charge. The structures with one and two double bonds both minimize formal charge but do not obey the octet rule. Of these two, the structure with one double bond is preferred because the formal charge is localized on the more electronegative oxygen atom. 210