How many of the following oxides are basic oxides?
 $ C{O_2} $ , $ Sn{O_2} $ , $ PbO $ , $ Pb{O_2} $ , $ P{b_3}{O_4} $ , $ A{l_2}{O_3} $

Hint: Study the given compounds carefully. Determine which elements are electropositive based on their positions in the periodic table. The nature of the oxides can be determined from there. Metals form basic oxides while non-metals form acidic oxides.

Complete step by step solution:
The electropositive character of the oxide's central atom will determine whether the oxide will be acidic or basic. The more electropositive the central atom, the more basic the oxide. The more electronegative the central atom, the more acidic the oxide. Electropositive character increases from right to left across the periodic table and increases down the column. The trend of acid-base behaviour is from strongly basic oxides on the left-hand side to strongly acidic ones on the right, via an amphoteric oxide (aluminium oxide) in the middle. An amphoteric oxide is one that shows both acidic and basic properties. This trend applies only to the oxides of the individual elements in the highest oxidation states for those elements. The pattern is less clear for other oxides.
Oxygen is very electronegative, so it should always be $ \delta - $ . But the electronegative atom will allow less electron density to be drawn away by the oxygen, so there will be less of a negative charge on the oxygen. This means that displacing the proton to give the oxygen more of a negative charge becomes more favourable. Thus, the oxide is acidic.
 $ C{O_2} $ and $ Sn{O_2} $ are acidic oxides.
Amphoteric oxides are classified as metal oxides that react with both acids as well as bases to create salts and water.
 $ PbO $ and $ A{l_2}{O_3} $ are amphoteric oxides. They can act as a base or acid.
For the electropositive atom, oxygen now almost gets that atom’s entire electron density. This means that oxygen is just a tad too negative to feel well, so it will draw protons out of the surrounding solution to protonate itself. Thus, the oxide is basic.
​ $ Pb{O_2} $ and $ P{b_3}{O_4} $ are basic oxides.
Thus, two oxides are basic oxides.

Note:
Since the acidity of a cation rises rapidly with charge, d-block elements that exhibit a wide variety of oxidation numbers may have one or more oxides that exhibit only basic properties and one or more oxides that exhibit only acidic properties. The higher the oxidation number, the more acidic the corresponding oxide.