Which of the following metals is classified as a noble metal?

Gold is classified as a noble metal because of its exceptional resistance to corrosion and oxidation. Noble metals are known for their stability and do not easily react with other elements, which allows them to maintain their luster and integrity over time. This characteristic is due to their electron configuration, which makes them less likely to participate in chemical reactions that would lead to deterioration or tarnishing.

Other metals, such as aluminum, iron, and zinc, do not share these properties. Aluminum can oxidize when exposed to air, forming a protective layer but is not considered a noble metal due to its reactivity. Iron is prone to rust when it reacts with moisture and oxygen, and zinc, while somewhat resistant to corrosion, can still oxidize more readily compared to noble metals. This fundamental difference in chemical behavior and stability under environmental conditions highlights why gold is classified as a noble metal.