Here's why:

* Ionic Compound: Copper II oxide is an ionic compound, meaning it is formed by the electrostatic attraction between positively charged copper ions (Cu²⁺) and negatively charged oxide ions (O²⁻).

* Strong Bonding: The strong ionic bonds between these ions give copper II oxide a rigid structure, making it solid at room temperature.

* Melting Point: Copper II oxide has a relatively high melting point of 1200 °C (2192 °F), further indicating its solid state at room temperature.