Are ionic bonds the strongest type of bonds?
Just to address this old question....the answer is NO.....
Ionic compounds TEND to have high melting and boiling points...why? Because ionic compounds ARE NON-MOLECULAR...i.e. an ionic compound consists of an infinite array of positive and negative ions that are held together by STRONG electrostatic forces.
An isolated ion in the lattice is attracted to every counterion in the lattice by Coulomb's law of electrostatic attraction. Of course it is also repelled by very other ion of the SAME charge, but if you add all the forces of attraction and repulsion up over the entire lattice, which may certainly be done quantitatively, you can get an estimate of the lattice enthalpy...and this is very ATTRACTIVE....
Now materials composed of discrete molecules tend to have intrinsically low melting and boiling points, because their molecular, their discrete particle nature, facilitates separation of the individual molecules....
On the other hand, there are material that are NON-MOLECULAR, but in which the constituent atoms are bound together by STRONG COVALENT bonds in an infinite array....that persists thruout the entire covalent lattice... And the goto example is silicon dioxide
On the other, other hand, there are metals that are bound together by metallic bonding....and even here some metals can be room temperature liquids....what are the examples?