Non-metals form acidic oxides because they react with water to produce acids. This is because non-metals have the ability to release electrons when they react with other substances. When they react with water, they donate electrons to the water molecules, which then split into hydrogen ions (H+) and hydroxide ions (OH-). The excess hydrogen ions cause the solution to become acidic.

For example, when carbon dioxide (CO2), a non-metal oxide, reacts with water, it forms carbonic acid (H2CO3):

CO2 + H2O → H2CO3

Carbonic acid is a weak acid that releases hydrogen ions when it dissociates in water. The resulting hydrogen ions cause the solution to become acidic.

In contrast, metal oxides form basic oxides because they react with water to produce bases. This is because metals have the tendency to attract electrons when they react with other substances. When they react with water, they receive electrons from the water molecules, which then split into hydrogen ions (H+) and hydroxide ions (OH-). The excess hydroxide ions cause the solution to become basic.

For example, when sodium oxide (Na2O), a metal oxide, reacts with water, it forms sodium hydroxide (NaOH):

Na2O + H2O → 2NaOH

Sodium hydroxide is a strong base that releases hydroxide ions when it dissociates in water. The resulting hydroxide ions cause the solution to become basic.