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Solutions to Problems 5 δ⁺ (f) H:N::N:H Double bond between nitrogens. H δ⁺ (g) H:C::C::0: A molecule with two double bonds. + (h) H:N::N::N: H:N:N:::N: (i) Major (O more electronegative than N) 26. The symbols δ⁺ and δ⁻ are written above or below the appropriate atoms in the answers to Problem 25 above. In each polar bond, the more electropositive atom is designated δ⁺, and the more electronegative atom δ⁻, based on the electronegativities in the periodic table. 27. (a) H:- Hydride ion. Contrast (a proton) and H (H atom). H (b) H:C:- A carbanion. C has an octet and a - 1 charge. H H (c) A carbocation. C has only a sextet and a +1 charge. H H (d) A carbon "radical." C is neutral, bonded to only three other atoms, and surrounded by 7 electrons. H HH (e) H:C:N:H The methylammonium cation. The product of CH₃NH₂ + Compare + HH H (f) H:C:O: Methoxide ion. The product of ionization of methanol, CH₃O⁻ + Compare H H2O + H (g) H:C: A "carbene." A neutral carbon, bonded to two other atoms, with only a sextet of electrons. (h) Another carbanion. Carbanions [(b) and (h)], carbocations (c), free radicals (d), and carbenes (g) are reactive species of high energy. They can, however, function as reaction "intermediates." (i) Hydrogen peroxide. 28. How to begin? Look at each atom and compare the bonding pattern with simpler structures that are more familiar to you. Count bonds. Count electrons. This exercise will make it easier for you to recognize similar situations later (as in exams). Then do the formal charge determination as described in the text. (a) The oxygen has three bonds and a lone pair. What simpler species do you know that is similar? Hydronium ion is one, probably the simplest. We've already seen the formal charge determination +1 for the oxygen in hydronium ion, based upon the calculation 6 (group # for O) - [3 (half of shared e- in bonds) + 2 (unshared e⁻)] = +1