Since the atomic number of an element is 12 then its electronic configuration is 2, 8, 2. It has 2 electrons in valence shell so it is a metal. And we know that oxide of metal are basic in nature. Hence its oxide is basic.

Note- Non-metals always gain electrons and metals loose their electrons.

Note- Oxides of metals are basic in nature and oxides of non-metals are acidic in nature.