Ionic vs. Covalent Bonds: Understanding Electronegativity Differences

[devanlevin]

in chemistry, how do i know when there is an ionic bond and when a covalent bond, someone told me when the difference between two atoms electronegativity is more than 2.5 there is an ionic bond, but there are molecules with differences in its atoms electroegativity less than 2.5m such as MgO or NaCl

 

[chemisttree]

There is no clear demarcation between the two. There usually exists some character of both types of bonding in any given bond. Electronegativity differences can be used as an ad hoc method to describe the type but it is http://www.chem1.com/acad/webtut/bonding/polcov.html"