If the resonance energy of C-H bond is 24.3 kilo joule per mole the electronegativity difference of C and H is
Answers
Answer:
Explanation:
gives you two possibilities for χF, 0.4 or 3.8, depending on whether the quantity (2.1−χF) is positive or negative. This is where we need to use some knowledge of chemistry: fluorine is more electronegative than hydrogen, so we should have χF>χH, and consequently we take the solution χF=3.8.
Why should bond energies be related to electronegativity? The idea that Pauling had when he devised this equation was that in a covalent bond between two of the same atom, there is no electronegativity difference and hence no ionic contribution to the bond strength. Hence, the "average covalent contribution" of each atom to a bond could be measured by the mean of the two bond strengths, i.e. [Ed(A−A)+Ed(B−B)]/2.
However, when there is a difference in electronegativity, the bond strength has an ionic contribution. The larger the difference in electronegativity |χA−χB|, the larger the ionic contribution. This ionic contribution could be roughly measured by subtracting the covalent contribution, [Ed(A−A)+Ed(B−B)]/2, from the A−B bond strength.