Final answer:
Yes, it has been observed that metals tarnish when they react with oxygen to form an oxide layer, which reduces their reactivity. This is due to a process called oxidation, and the tarnish usually serves as a protective barrier. Corrosion resistance varies among metals, and preventing or controlling it is a significant field of study.
Step-by-step explanation:
Oxidation and Corrosion of Metals
Yes, the observation that metals tarnish due to the formation of an oxide layer is well-documented. Atoms on the surface of a metal react with the oxygen in the air to form an oxide coating. This process is known as oxidation, and the resulting layer can appear dull and decrease the metal's reactivity by acting as a barrier to further chemical interactions. For instance, iron develops rust (an iron oxide), while aluminum's reaction with oxygen results in a thin, protective aluminum oxide layer. Corrosion, which includes rusting and tarnishing, is generally a REDOX (oxidation-reduction) process, where metals lose electrons and oxygen gains them.
Different metals exhibit varying levels of corrosion resistance. Gold and platinum, for example, are highly resistant to oxidation. Others like aluminum and copper develop a protective oxide layer or patina that shields the metal beneath from further environmental assault. The process of corrosion is not just limited to reactions with oxygen; for example, silver can tarnish by reacting with sulfur in the air to form silver sulfide. Industrial research continually seeks methods to prevent corrosion, with significant commercial implications, as corrosion can lead to substantial economic costs.