Copper sulfide (CuS) is an ionic compound. It consists of positively charged copper ions (Cu2+) and negatively charged sulfide ions (S2-). These ions are held together by strong electrostatic forces, forming a stable ionic lattice. The ionic nature of CuS is evident from its high melting point (1130 °C) and boiling point (1650 °C), as well as its solubility in polar solvents like water. In contrast, molecular compounds are formed by the covalent bonding of atoms, and typically have lower melting and boiling points and are soluble in non-polar solvents.