The compound ZnO is an ionic solid. To understand why ZnO is an ionic solid, we need to look at the elements that make up the compound. ZnO consists of zinc Zn and oxygen O atoms. Zinc is a metal, and it is found in Group 12 of the periodic table. Oxygen, on the other hand, is a non-metal and is found in Group 16 of the periodic table. Ionic compounds generally form when a metal reacts with a non-metal. In this case, zinc, being a metal, loses electrons to form a positively charged ion cation , while oxygen, being a non-metal, gains electrons to form a negatively charged ion anion . Specifically, zinc loses two electrons to form a Zn ion, and oxygen gains two electrons to form an O ion. These ions are attracted to each other due to their opposite charges, forming an ionic bond.The resulting ionic solid, ZnO, has a crystalline structure in which the Zn and O ions are arranged in a regular, repeating pattern. This structure is held together by the strong electrostatic forces between the positively charged zinc ions and the negatively charged oxygen ions. These forces are responsible for the high melting and boiling points, as well as the brittleness, of ionic solids like ZnO.In summary, ZnO is an ionic solid because it is formed by the reaction between a metal zinc and a non-metal oxygen , resulting in the formation of oppositely charged ions that are held together by strong electrostatic forces in a crystalline structure.