Which element from following rapidly loses its its luster in air and tarnishes?
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Alkali metals (Group 1) are highly reactive and readily oxidize in air, losing their luster. Their reactivity generally increases down the group. Alkaline earth metals (Group 2) are also reactive but often form a stable protective oxide layer. Transition metals vary in reactivity, with some being quite noble (resistant to tarnishing) and others forming stable oxide layers.