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9 Molecular Geometry Solutions to Exercises 9.80 (a) Substances with unpaired electrons are attracted into a magnetic field. This property is called paramagnetism. (b) Weigh the substance normally and in a magnetic field, as shown in Figure 9.44. Paramagnetic substances appear to have a larger mass when weighed in a magnetic field. (c) See Figures 9.35 and 9.43. O₂⁺, one unpaired electron; two unpaired electrons; Li₂⁺, one unpaired electron 9.81 1 (a) B₂⁺ (b) Li₂⁺ (c) N₂⁺ (d) increase increase increase decrease Addition of an electron increases bond order if it occupies a bonding MO and decreases stability if it occupies an antibonding MO. 9.82 Determine the number of "valence" (non-core) electrons in each molecule or ion. Use the homonuclear diatomic MO diagram from Figure 9.43 (shown below) to calculate bond order and magnetic properties of each species. The electronegativity difference between heteroatomics increases the energy difference between the 2s AO on one atom and the 2p AO on the other, rendering the "no interaction" MO diagram in Figure 9.43 appropriate. (a) CO+: B.O. = 2) / 2 = 2.5, paramagnetic (b) NO-: 12 B.O. = 4) / 2 = 2.0, paramagnetic (c) OF+: B.O. = 4) / 2 = 2.0, paramagnetic (d) B.O. = 6) / 2 = diamagnetic 9.83 Analyze/Plan. Determine the number of "valence" (non-core) electrons in each molecule or ion. Use the homonuclear diatomic MO diagram from Figure 9.43 (shown below) to calculate bond order and magnetic properties of each species. The electronegativity 256