The correct option is Silver and gold.
Explanation
Metals react with oxygen to form metal oxides. However, the reactivity of metals towards oxygen varies significantly based on their position in the reactivity series (activity series). Metals placed at the bottom of this series possess very low chemical reactivity and do not easily lose electrons to form bonds with oxygen.
Analysis of Metal Reactivity
- Sodium and Potassium: These are highly reactive alkali metals located at the top of the reactivity series. They react vigorously with oxygen even at room temperature and can catch fire if exposed to air.
- Zinc and Aluminium: These are moderately reactive. At room temperature, they form a thin protective oxide layer. Upon heating, they react with oxygen; for example, zinc burns to form zinc oxide.
- Copper and Iron: These metals react with oxygen only upon heating. Iron does not burn as a solid mass, though iron filings burn vigorously. Copper does not burn but forms a black coating of copper(II) oxide when heated significantly.
- Silver and Gold: These are noble metals situated at the bottom of the reactivity series. They show negligible reaction with oxygen and do not oxidize even at high temperatures. This chemical inertness preserves their luster.
Key Takeaway: Noble metals such as silver (Ag) and gold (Au) are chemically inert towards oxygen and do not corrode or form oxides even when subjected to high heat.