Question

Which alkaline earth is the strongest reducing agent?

Answer 1

Hint : A reducing agent is a chemical species or reactant capable of reducing another species and itself getting readily oxidized in the process. Therefore a stronger reducing agent will quickly undergo oxidation and lose its electrons.

Complete Step By Step Answer:
Oxidation is defined as the process of gaining oxygen atoms or losing electrons and reduction is the process of gaining hydrogens, losing oxygen atoms or accepting electrons.
A reducing agent is a substance that undergoes self-oxidation and facilitates the reduction of another chemical species by donating its electrons.
Alkaline earth metals are elements placed in the second group of the periodic table. These electropositive elements have two electrons in their valence shell that they readily give away.
The ability to act as a strong reducing agent is dependent on the metal’s ability to give away electrons. On descending the second group of alkaline earth metals, the size of atoms goes on increasing along with a reduction in their ionization energies as a consequence of increasing the number of intervening shells that reduce the effective nuclear charge experienced by the outermost electrons. Thus, the alkaline earth metals can be arranged in an increasing order of their reducing strength in the following manner:
$Be < Mg < Ca < Sr < Ba$
Barium being the largest non-radioactive atom in the group with the lowest ionization energy easily loses its electrons and is therefore the strongest reducing alkaline earth metal.

Note :
The order of increasing ability to act as a reducing agent in alkali metals is different from that observed for alkaline earth metals. The exceptional behavior shown by lithium is due to its high hydration enthalpy which is not the case for beryllium.