Introduction:

Gold and platinum are known for their resistance to corrosion, even in moist air. This unique property is due to several factors that contribute to their stability and inertness.

1. Noble Metals:

Gold and platinum are classified as noble metals, which means they are resistant to oxidation and corrosion compared to other metals. This is due to their electronic configuration, specifically the presence of filled d- and f-orbitals in their outermost energy levels.

2. Lack of Reactivity:

Gold and platinum have low reactivity with the environment, making them less prone to corrosion. This can be attributed to their high standard reduction potentials, indicating their ability to readily gain electrons and resist oxidation. As a result, they are less likely to undergo chemical reactions with moisture, oxygen, or other elements present in the air.

3. Protective Oxide Layers:

Both gold and platinum form thin oxide layers on their surfaces when exposed to air. These oxide layers act as a protective barrier, preventing further oxidation and corrosion. In the case of gold, a thin layer of gold oxide forms, which is insoluble in water and prevents the metal from reacting with moisture. Platinum, on the other hand, forms a thin layer of platinum dioxide (PtO2) which also acts as a protective film.

4. High Density and Malleability:

Gold and platinum have high densities and are malleable, which means they can be easily shaped without cracking or breaking. This property allows them to maintain their structural integrity even when exposed to moisture or other environmental factors, reducing the likelihood of corrosion.

5. Lack of Reactive Impurities:

Gold and platinum are often found in their pure form or with very few impurities. These impurities, when present in other metals, can increase their reactivity and susceptibility to corrosion. However, the absence of reactive impurities in gold and platinum contributes to their resistance to corrosion.

Conclusion:

Gold and platinum resist corrosion in moist air due to their noble metal properties, lack of reactivity, formation of protective oxide layers, high density and malleability, as well as the absence of reactive impurities. These factors work together to maintain the integrity and inertness of gold and platinum, making them highly desirable for various applications, including jewelry and industrial use.