In a comparison of reactivity, which is more reactive: Iron or Calcium?

Calcium is more reactive than iron due to its position in the reactivity series of metals. The reactivity series arranges metals based on their ability to displace other metals from compounds and their tendency to participate in chemical reactions.

Calcium is an alkaline earth metal, located in Group 2 of the periodic table, where metals are generally more reactive. Its reactivity is primarily attributed to its atomic structure, which features two electrons in its outer shell. Calcium readily loses these two electrons to achieve a stable electron configuration, allowing it to react easily with water, acids, and oxygen.

Iron, on the other hand, is located further down the series as a transition metal and is less eager to lose electrons compared to calcium. Although iron does react with acids and water, the reactions are not as vigorous as those of calcium. Additionally, iron tends to form rust (iron oxide) when exposed to moisture and oxygen, which illustrates that while it does react, it does so less readily than calcium.

Therefore, calcium's greater reactivity is a result of its position in the periodic table and its ability to lose electrons more easily than iron.