Explanation:

Metals generally form basic oxides because of their tendency to lose electrons and form cations. When metals react with oxygen, they form metal oxides. The nature of these metal oxides depends on the reactivity of the metal and the conditions under which the reaction takes place.

Basic Oxides:
When metals react with oxygen, they form metal oxides. Metal oxides are generally basic in nature because they react with acids to form salts and water. Basic oxides are also called alkaline oxides. They have a pH value greater than 7 and turn red litmus paper blue.

Examples of basic oxides:
- Sodium oxide (Na2O)
- Magnesium oxide (MgO)
- Calcium oxide (CaO)
- Barium oxide (BaO)

Acidic Oxides:
Non-metals generally form acidic oxides because of their tendency to gain electrons and form anions. Acidic oxides react with bases to form salts and water. They have a pH value less than 7 and turn blue litmus paper red.

Examples of acidic oxides:
- Carbon dioxide (CO2)
- Sulfur dioxide (SO2)
- Nitrogen dioxide (NO2)
- Phosphorus pentoxide (P2O5)

Neutral Oxides:
Some metal oxides are neutral in nature. They neither react with acids nor with bases. They have a pH value of 7 and do not change the colour of litmus paper.

Examples of neutral oxides:
- Carbon monoxide (CO)
- Nitric oxide (NO)
- Water (H2O)

Therefore, metals generally form basic oxides due to their tendency to lose electrons and form cations.