The two that won't are C and O. They will react, but not ionically. O is on the left of the Periodic table and C is more or less in the middle. They form CO carbon Monoxide and CO2 which is Carbon Dioxide. They are just not ionic.
Carbon and Oxygen cannot react to form an ionic compound because the two elements are non-metals. To form an ionic bond, a metal combines with a non-metal through electrostatic attraction of oppositely charged ions.
