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9 Molecular Geometry Solutions to Exercises + (c) A node is generated in because antibonding MOs are formed when AO lobes with opposite phases interact. Electron density is excluded from the internuclear region and a node is formed in the MO. (d) Sc: [Ar]4s²3d¹ Omitting the core electrons, there are six in the energy level diagram. σ³ᵈ 4s 4s (e) The bond order in Sc₂ is 1/2 (4 - 2) = 1.0. 9.116 (a) The molecular and empirical formulas of the four molecules are: benzene: molecular, C₆H₆; empirical, CH napthalene: molecular, C₁₀H₈; empirical, C₅H₄ anthracene: molecular, empirical, C₇H₅ tetracene: molecular, empirical, C₃H₂ (b) Yes. Since the compounds all have different empirical formulas, combustion analysis could in principle be used to distinguish them. In practice, the mass % of C in the four compounds is not very different, so the data would have to be precise to at least 3 decimal places and 4 would be better. (c) C₁₀H₈(s) + (d) = 5D(C=C) + 6D(C-C) + 8D(C-H) + 12D(O=O) - 20D(C=O) - 8D(O-H) = 5(614) + 6(348) + 8(413) + 12(495) - 20(799) - 8(463) = 271