Which property is best to use when determining the strength of an ionic bond in a solid?

I think the best property to use is electronegativity since that is how much it attracts/wants electrons.  The larger the difference in electronegativity is between two atoms, the stronger the ionic bond will be.  This is also why two atoms need to have a minimum difference between the electronegativity to be considered ionic and not covalent.

the variance of 3,5,7,9,11 is 2