When a metal reacts with oxygen, it forms metal oxide. The nature of the oxide formed depends on the reactivity of the metal.

Explanation:

Reactivity of metals: Metals differ in their ability to react with oxygen, depending on their position in the reactivity series.

Reactivity series of metals: The reactivity series of metals is a list of metals arranged in the order of their decreasing reactivity with oxygen. The most reactive metal is placed at the top of the series, and the least reactive metal is placed at the bottom of the series.

The reactivity series of metals is as follows:

Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminium (Al) > Zinc (Zn) > Iron (Fe) > Tin (Sn) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Silver (Ag) > Gold (Au)

When a metal reacts with oxygen, it forms metal oxide. The nature of the oxide formed depends on the reactivity of the metal.

Basic oxides: Metals that are more reactive than hydrogen (H) react with oxygen to form basic oxides. Basic oxides are also called alkaline oxides. They are soluble in water and turn litmus paper blue. Examples: Sodium oxide (Na2O), Calcium oxide (CaO), Magnesium oxide (MgO), Aluminium oxide (Al2O3), Potassium oxide (K2O).

Neutral oxides: Metals that are less reactive than hydrogen (H) react with oxygen to form neutral oxides. Neutral oxides are neither acidic nor basic. They do not show any effect on litmus paper. Examples: Zinc oxide (ZnO), Iron oxide (Fe2O3), Tin oxide (SnO2), Lead oxide (PbO).

Acidic oxides: Metals that are very less reactive or non-reactive with oxygen do not form oxides when they react with oxygen. However, metals like copper (Cu) and silver (Ag) form oxides that are acidic in nature. Acidic oxides react with water to form acidic solutions. For example, copper oxide (CuO) is an acidic oxide.

Conclusion:

The nature of the oxide formed when a metal reacts with oxygen depends on the reactivity of the metal. Metals that are more reactive than hydrogen (H) form basic oxides. Metals that are less reactive than hydrogen (H) form neutral oxides. Metals that are very less reactive or non-reactive with oxygen do not form oxides, except for copper (Cu) and silver (Ag), which form acidic oxides.