课程名称︰化学键 课程性质︰选修 课程教师︰王瑜 开课学院：理学院 开课系所︰化学系 考试日期（年月日）︰98/4/17 考试时限（分钟）：100分钟+10分钟延长 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1.Work out the molecular orbitals of A2; write down electronic configuration, bond order and magnetic property of B2, C2 and O2. Compare the bond order and bond distance of NO, NO+ and NO-. 2.Describe the molecular orbitals (MO) of planar cyclo-H5 and -H6 in terms of two fragments as H3 + H2 and H3 + H3. 3.Work out the MOs of CH4 in tetrahedral and seesaw shape (with a linear CH2 part) respectively; plot the orbital correlation and predict the geometry of CH4, CH4(+), CH4(2+). 4.The π electron energy of butadiene is lower than that of cyclobutadiene, but it is just the opposite for hexatriene and benzene case, explain. What is the condition for aromaticity of planar cyclo-CnHn? Why? What is the res- onance (delocalization) energy of benzene in terms of β, assuming α+βfor ethylene? The orbital energy of cyclo CnHn, CnH(n+2) are as following: Cyclo-CnHn: Ei = α+2βcos(2jπ/n) where j = 0, ±1, ±2,... -2┌ __ ─ ≡ │ ─ ¯¯ ≡ -1│ ─ ─ ─ ≡ │ ─ __ ≡ 0│─ ─ ─ __ ≡ │ ─ ≡ 1│ ─ ─ __ ≡ │ ─ __ ≡ 2└ ¯¯ ─ ≡ CnH(n+2): n 1 2 3 4 5 6 ∞ 5.Given the orbital correlation diagram of AH2 between the linear and bent case below; explain why the bent angle of H-A-H is 119, 92 and 92 for A = Al, Si and P respectively. Predict the geometry of each dication AH2(2+). (Figure: orbital correlation diagram of AH2 between the linear and bent case) --

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