* Strong electrostatic attraction: Ionic bonds are formed by the strong electrostatic attraction between oppositely charged ions. This strong attraction makes it difficult to break the bond.

* High melting and boiling points: The high melting and boiling points of ionic compounds reflect the strength of the ionic bonds.

* Brittle nature: Ionic compounds are often brittle because the strong, rigid structure makes it difficult to deform. If a stress is applied, the ions shift, causing a disruption in the electrostatic attraction and leading to a fracture.

However, there are some exceptions:

* Large ions: Ionic bonds involving large ions (with larger ionic radii) can be weaker due to the weaker electrostatic attraction between the ions.

* Polarizability: Some ions can be more polarizable than others. This means that the electron cloud around the ion can be distorted more easily, which can lead to a weaker ionic bond.

Overall, ionic bonds are generally considered hard due to the strong electrostatic forces involved. However, there are some exceptions where ionic bonds can be softer depending on the specific ions involved.