Because known compounds with N€“I bonds tend to be unstable, there are no thermodynamic data available with which to calculate the N€“I bond energy. However, we can estimate a value from Pauling€™s formula relating electronegativities and bond energies (see Problem 9.137). Using Pauling€™s electronegativities and the bond energies given in Table 9.5, calculate the N€“I bond energy.

Problem 9.137
According to Pauling, the A€“B bond energy is equal to the average of the A€“A and B€“B bond energies plus an energy contribution from the polar character of the bond:
BE(A€“B) = 1/2 [BE(A€“A) + BE(B€“B)] + k(XA XB)2]
Here XA and XB are the electronegativities of atoms A and B, and k is a constant equal to 98.6 kJ. Assume that the electronegativity of H is 2.1. Use the formula to calculate the electronegativity of oxygen.

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TABLE 9.5 Bond Energies (in kJ/mol) Single Bonds 0 Cl Br H 432 C 41 346 N 386 305 167 O 459 358 201 142 S 363 272_ F 565 485 283 190 284 155 CI 428 327 313 218 255 249 240 Br 362 28520 217 249 216 190 226 ー 295 213 201 278 208 175 149 Multiple Bonds CーС 602 C_N 615 C-O C C 835 C N 887 C O N-N 418 N O 607 S-O (in SO2) N N 942 0- 44 S-O (in SO3) 469 745 (799 in CO2) 1072 532