Question

Good reducing agents belong to:
(A) Group IA
(B) Group IIA
(C) Group IIIA
(D) Group VIA
(E) Group VIIA

Answer 1

Hint :Reducing agents are the active elements that undergo oxidation, where they lose (donate) electrons and reduce the other element. Looking at period trends, some elements can lose electrons easier than other elements.

Complete Step By Step Answer:
A reducing agent is any substance that loses its electron to other substances in a redox reaction and gets oxidised itself.
Simply put, it reduces the other elements by giving out electrons.
Atoms, ions and molecules that can easily lose their electrons make good reducing agents.
All good reducing agents have a low electronegativity. Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. Therefore a low electronegativity implies they can give away electrons easier than other atoms.
Also, good reducing agents have very small ionization energies which is the amount of energy an electron has to absorb to come out of the influence of the nucleus. Thus a low ionization energy ensures that electrons can leave the atoms without much energy required to do so.
Across a period, the size of the atom decreases which in turn increases the effective nuclear charge. This makes the electrons get tightly held to the nucleus.
Therefore, reducing agents are stronger in lower group numbers.
With all these points, the answer to this question is (A) group IA.
Group IA contains alkali metals which are very reactive, and have only one electron in their valence shell. This allows them to lose that one electron easily.
Also, they are the largest atoms (atomic size) which implies a lower nuclear charge on the outermost electron.
Therefore, good reducing agents belong to group IA (Option (A)).

Additional Information:
Across the period, oxidising ability increases. Therefore in the options given above, good oxidising agents would belong to group VIIA.

Note :
Such questions require your knowledge on periodic trends along with an understanding of redox reactions. Components of redox reactions (reduced and oxidised substances, reducing and oxidising agents) are important. Also, you need to know how to identify such substances in a redox reaction.