Question

a solid melts at 840 °c and conducts electricity when liquid. which of these is a property of this ionic compound? high melting point malleable shiny luster

Explanation:

Ionic compounds have strong electrostatic forces between ions. This results in high melting points as a lot of energy is needed to break these forces. Malleability (ability to be hammered into shape) and shiny luster are properties of metals, not ionic compounds.

Answer:

high melting point