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.

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 217 249 216 190 226 295 213 201 278 208 175 149 Multiple Bonds C 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