My textbook says that interhalogen compounds are more reactive than halogens, because the $\ce{X-X}$ bond in halogens (for example, dichlorine or $\ce{Cl2}$) is stronger than the $\ce{X-X'}$ bond in interhalogens (for example, chlorine monofluoride or $\ce{ClF}$).
(In the symbols that I have used, $\ce{X}$ and $\ce{X'}$ have been used to denote dissimilar halogen atoms.)
So my question is: why is the bond between dissimilar halogens weaker than the bond between atoms of the same halogen?
I am aware that the bond between two identical atoms will be a completely covalent bond due to no difference in the electronegativities of the participant atoms. So, the $\ce{X-X}$, bond as in $\ce{Cl2}$ will have no ionic character.
In case of an interhalogen compound, however, the difference in the elecronegativities of the (dissimilar) participant atoms will cause the bond to become polar and thereby acquire ionic character.
So is it the ionic character of the interhalogen compounds that causes them to be more reactive than halogens? But then, this means that ionic bonds are weaker than covalent bonds.
But, the answers here as well as here say that an ionic bond is stronger.
But this link says the very opposite. Okay, the people writing the answers there have written it to suit an eight grader's understanding, but even so, they have stated that covalent bonds are stronger than ionic bonds.
So which alternative am I to believe? I know that most bonds are neither purely ionic not purely covalent, but intermediate between these two extreme characters, but this only serves to increase my bewilderment.
Can somebody please resolve this, or tell me where I have gone wrong in my reasoning as regards the reactivities of the interhalogen compounds in comparison with halogens?
And finally, please tell me the reason why interhalogens are more reactive. Thanks!
