When comparing the chemical reactivity of calcium (Ca) and barium (Ba), it is essential to consider their positions in the periodic table. Calcium is located in Group 2 (the alkaline earth metals) and has the atomic number 20, while barium is in the same group but has the atomic number 56.
Generally, as you move down a group in the periodic table, the reactivity of the elements increases. This trend is primarily due to the increasing size of the atoms and the greater distance of the valence electrons from the nucleus. In the case of alkaline earth metals, both Ca and Ba have two valence electrons, but barium’s larger atomic radius means that its valence electrons are farther from the nucleus and are therefore more easily lost in chemical reactions.
As a result, barium (Ba) is more chemically reactive than calcium (Ca). It reacts more vigorously with water and acids compared to calcium. Thus, when evaluating their reactivity in chemical reactions, barium should be considered the more reactive element.