There are a number of things to consider when thinking about this:1. Ionic bonds are generally strong due to the attraction of oppositely charged ions. Covalent bonds are also strong due to the attraction from each nuclei to the valence electrons.2. However the intermolecular bonds in most covalent compounds are very weak, they often only have instantaneous-induced dipole bonding, so will exist as gases at room temp.3. Ionic compounds exist in giant lattice structures rather than diatomic molecules so will exist as solids with high melting points.4. However some covalent compounds can exist as a giant covalent network, such as in diamond. This is where all carbon atoms are bonded to 4 other carbon atoms and this makes a very strong compound with extremely high melting points.However, in terms of the pure strength of the intra-molecular bonds (between atoms in a molecule), covalent bonds are stronger.