Final answer:
The most reactive element in the reactivity series is found at the top for metals and at the top of the nonmetal Halogen series with fluorine being the most reactive. These series help predict the outcomes of reactions, particularly displacement reactions where more reactive elements displace less reactive ones.
Step-by-step explanation:
In the reactivity series or activity series of metals, the most reactive element is found at the top of the series. The elements are listed in decreasing order of their reactivity, meaning those that are easiest to oxidize or lose electrons are placed higher. For instance, metals like lithium and potassium are at the very top of the series and are extremely reactive. On the flip side, the least reactive metals, such as gold and platinum, are positioned at the bottom.
Halogens have their own activity series, with fluorine being the most reactive nonmetal, typically positioned at the top of the series for nonmetals. Noble gases are not usually placed in the activity series as they are inert. Thus, the answer is (A) At the top.
The reactivity series is essential in predicting the outcomes of reactions, especially in displacement reactions where a more reactive element displaces a less reactive element from a compound. For example, a metal high on the activity series can displace a metal lower down the series from its compounds.