Which of the following metals is considered passive?

Gold is considered a passive metal due to its high resistance to corrosion and oxidation. This characteristic arises from the formation of a stable, inert oxide layer that forms on its surface when exposed to the environment. This oxide layer prevents further reaction with the surrounding elements, resulting in a material that maintains its luster and integrity over time.

In contrast, iron can undergo significant corrosion, especially in the presence of moisture, as it readily oxidizes to form rust. Copper, while more resistant to corrosion than iron, can still tarnish and oxidize over time, particularly in the presence of sulfur compounds. Lead can also oxidize, although it forms a protective oxide layer that can slow further corrosion, but it is not as inert as gold. With its remarkable stability and resistance to environmental degradation, gold stands out as the prime example of a passive metal.