Which is the most reactive metal?

Explanation

Among the given options, as per the reactivity series, potassium (K) is the most reactive metal. It reacts vigorously with air and water, producing a large amount of heat. The ionization energy of potassium is lower than that of sodium because its atomic size is larger. Metals like potassium and sodium react rapidly with cold water. Their reactions are vigorous and exothermic because the released hydrogen ignites immediately. Calcium reacts with water relatively slowly. Magnesium does not react with cold water, but with hot water it produces magnesium hydroxide and hydrogen gas. Metals like aluminium, iron, and zinc do not react with cold or hot water; rather, they react with steam to produce metal oxides and hydrogen. Metals at the top of the reactivity series (K, Na, Ca, Mg, and Al) are so reactive that they are generally not found in the free state. (388)