The order of oxides in increasing basicity is CuO < Al₂O₃ < MgO < Na₂O.
The basicity of metal oxides is fundamentally linked to the metallic character of the element they contain. As metallic character increases, the tendency of an oxide to react with an acid (acting as a base) also increases.
Based on the provided reference, the metallic character of the elements listed decreases in the following sequence:
- Na > Mg > Al > Cu
Following this trend, the reference explicitly states that the basicity of the oxides of these elements decreases in the same order:
- Na₂O > MgO > Al₂O₃ > CuO
This means that sodium oxide (Na₂O) is the most basic among this set, while copper oxide (CuO) is the least basic.
Determining the Increasing Order
To present the oxides in order of increasing basicity, we simply reverse the sequence provided for decreasing basicity.
Here is the list ordered from the oxide with the lowest basicity to the oxide with the highest basicity:
- CuO (Lowest Basicity)
- Al₂O₃
- MgO
- Na₂O (Highest Basicity)
This relationship can be clearly shown using comparison symbols:
CuO < Al₂O₃ < MgO < Na₂O
This order reflects the decreasing metallic character from left to right across the elements Na, Mg, Al, and Cu. Generally, oxides of alkali metals (like Na₂O) are strongly basic, oxides of alkaline earth metals (like MgO) are basic, oxides of amphoteric elements (like Al₂O₃) exhibit both acidic and basic properties, and oxides of less metallic elements or transition metals (like CuO) tend to be weakly basic or even slightly acidic or amphoteric depending on the oxidation state.
