Which metal is more reactive, magnesium or lithium?

• A. Magnesium
• B. Lithium
• C. Sodium
• D. Calcium

Answer: (B)

Reactivity of metals is all about how easily a metal can lose electrons to form positive ions. The further up a metal is in its group, the more tightly its outer electrons are held, and the less reactive it tends to be; but alkali metals (-group 1) are especially reactive because they onlyhave one outer electron to lose. Among Li and Mg, lithium is an alkali metal, while magnesium is an alkaline earth metal that has to lose two outer electrons. This makes lithium easier to oxidize and thus more reactive overall. In practice, lithium’s lower first ionization energy means it can shed its outer electron more readily, so it reacts more vigorously with substances like water and acids than magnesium does. For example, lithium reacts readily with water to form lithium hydroxide and hydrogen, whereas magnesium reacts much more slowly with cold water (and more noticeably with steam). So lithium is the more reactive metal here.