The strength of covalent bonds depends on the degree to which the electrons are shared between the atoms involved in the bond.what determines the strength of covalent bonds that lead to bond energy values?
So take an SN2 reaction between methyl iodide and generic nucleophile Nuc-. Nuc- attacks and iodide leaves. Why does iodide leave and not a hydride? Because the heterolytic bond cleavage energy for a C-I bond is less than for a C-H bond. I is much more electronegative than C so the electrons in that bond already reside closer to the I. In contrast, C and H have similar electronegativities so the electrons in that bond reside in the middle of the C-H axis. Since the C-I electrons are already closer to the I, it's easier to move those electrons completely towards the I, thereby breaking the bond.Thank you! Do you mind explaining this part more? What do you mean by this?