Chalk is an ionic compound. which is a property of all ionic compounds that makes chalk particularly useful for writing on a chalkboard?

Hardness and brittleness

Explanation:

Ionic substances form crystal lattices which allow the compounds to be hard because of the strong attractions between positive and negative ions in the lattice. When pressure is applied to the compound like chalk , it may force ions of the same charge together ( i.e. positive to positive). This is called electrostatic repulsion which is able to break the crystal lattice allowing one to write on the chalkboard.

think its the third option