You guys need to distinguish between homolytic versus heterolytic bond strength, and crystal hardness versus true bond clevage.
This is a very good point. When we cleave an ionic bond, aren't we usually talking a heterolytic cleavage (i.e.-one atom (the nonmetal) is getting more electrons than the other)? I am guessing that homlytic cleavage is possible for ionic bonds (since anything is possible
), just extremely unlikely. Also, either could happen for covalent bonds (example, any binary acid). Crystal hardness is definitely not the same thing as bond cleavage energy, thay are measured in completely different ways.
Which brings me to my point, it is very difficult to compare the stregnths of ionic and covalent bonds. They are two different things, and the compounds they form have so many different properties, it is just not a striaght foward simple comparison.