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

Ionic compounds are made of positive and negative ions arranged in a crystal lattice. They are typically hard but brittle: the chalk can rub off in small particles when pressed against a chalkboard, leaving a visible mark. High melting point is also common for ionic compounds, but it does not explain chalk’s usefulness for writing.

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