What is the correct name for CaO?

The correct name for CaO is Calcium oxide. This name is derived from the elements that make up the compound: calcium (Ca) and oxygen (O). In nomenclature for ionic compounds, the name of the metal (in this case, calcium) is stated first, followed by the name of the non-metal (oxygen) with its suffix changed to "-ide."

Since calcium has a +2 charge as a cation and oxygen has a -2 charge as an anion, they combine in a 1:1 ratio to form the neutral compound CaO. Thus, the combination of calcium and oxygen is straightforwardly referred to as calcium oxide.

The other options do not accurately represent the correct naming conventions. For instance, 'Calcium dioxide' suggests there would be two oxygen atoms, which is not the case here. 'Oxide calcium' reverses the correct order of naming. Lastly, 'Calcium monoxide' inaccurately implies the presence of one oxygen atom but does not follow the standard nomenclature when only one oxide ion is involved. Therefore, Calcium oxide is the appropriate name adhering to chemical naming conventions.