Nitrogen forms single bonds with a variety of halogens
CHEMISTRY · Multi-part · CBSE · Chemistry · Chemical Bonding and Molecular Structure · Chemical Bonding and Molecular Structure
Problem
Nitrogen forms single bonds with a variety of halogens. A chemist considers the following set of bonds, all σ bonds in molecules where nitrogen is formally in the −3 oxidation state.
N–F, N–Cl, N–Br, N–I
Selected atomic radii (pm):
N 70 F 64 Cl 99 Br 114 I 133
Answer the questions below.
(a) Rank the four bonds from greatest to least average bond energy. Clearly explain the basis for your ranking.
(b) Without performing a numerical calculation, predict which of the four bonds would require the largest amount of energy per mole to homolytically cleave. Justify your answer with reference to both bond length and periodic trends.
(c) Suppose you are given that the bond energy of the N–Cl bond is 193 kJ mol⁻¹. Use your ranking in part (a) to estimate an approximate numerical range for the N–F bond energy. Explain how you arrived at the range.
(d) HF has a higher bond energy than F₂, even though both contain the F–F or F–H single bonds, respectively. Use concepts from parts (a)–(c) to propose a reason for this observation.