What characteristic is shown by the tarnishing of lithium in the presence of oxygen?

The tarnishing of lithium in the presence of oxygen illustrates that lithium, while being a reactive metal, forms an oxide layer slowly rather than rapidly. This slow tarnishing is primarily due to the formation of lithium oxide when lithium reacts with oxygen, which creates a protective barrier that slows further oxidation.

In the case of lithium, although it is a member of the alkali metals and is indeed reactive, it tends to tarnish at a rate that allows its surface to oxidize gradually rather than instantaneously. This characteristic is important in understanding the behavior of metals in air and how they interact with oxygen over time.

The specific nature of tarnishing also reflects on lithium's position in the reactivity series of metals, where it is reactive, but the rate at which it tarnishes demonstrates a moderate interaction with oxygen under standard conditions. This indicates that while reacivity is present, it is managed by the oxide layer formed as a result of the initial reaction, leading to a slow tarnishing process.