covalent bonds are stronger than ionic bonds.
Covalent bonds are much stronger because the covalent bond is formed by the sharing of electrons. The electrons from two different atoms share the orbital. This means that both electrons from the two different atoms now belong to both atoms. This binds the two atoms together.
Ionic bonds the electrons are not shared. One of the atoms with a much higher electron negativity basically takes the electron from the atom with the lower electron negativity. This leaves each atom as an ion. One atom becomes a negative ion, the other atom becomes a positive ion. The attraction between the two ions holds the atoms together but is easily broken.
However the intermolecular bonds in an ionic solid are very strong.
The negative ion can be attracted to (intermolecular bonded) to positive ions on all sides of the negative ion. In salt the negative chlorine is attracted six different positive ions. This makes solid salt very stable with a very high melting point.
The intermolecular bonds in covalent compounds are often very weak because the chemical are so strong. Carbon compounds such as methane and propane exist normally only as gases without almost no intermolecular bonds.
There is some overlap but, in general, ionic bonds are stronger than covalent bonds.
For example, one of the weakest covalent bonds is the
The ionic bond with the smallest lattice energy is in