Calcium is generally more reactive than magnesium due to its position in the periodic table and its atomic structure. Both elements are alkaline earth metals, but calcium is located below magnesium in Group 2 of the periodic table.
The reactivity of metals often increases as you move down a group. This trend can be attributed to the atomic size and the number of electron shells. Calcium has more electron shells than magnesium, which means its outermost electrons are further away from the nucleus. Specifically, calcium has four electron shells while magnesium has three.
As the distance between the nucleus and the outer electrons increases, the effective nuclear charge felt by these outer electrons decreases. This makes it easier for calcium to lose its two outer electrons during chemical reactions compared to magnesium, which holds onto its electrons more tightly because they are closer to the nucleus.
Additionally, calcium’s lower ionization energy, which is the energy required to remove an electron from an atom, contributes to its higher reactivity. The ionization energy for calcium is lower than that of magnesium, making it more likely to participate in chemical reactions.
In summary, the greater atomic size, lower ionization energy, and reduced nuclear attraction for the outer electrons in calcium compared to magnesium result in calcium being more reactive.