Problem 173 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following species involve \(\mathrm{M}-\mathrm{M}\) bond in addition to \(\mathrm{M}-\mathrm{O}\) bonds? (a) Carbon suboxide (b) Pyrosulphate ion (c) Pyrophosphoric acid (d) Dithionate ion

Step-by-Step Solution

Answer

The species with both M-M and M-O bonds are Pyrosulphate ion and Dithionate ion.

Step 1: Identify the Structure

First, let's identify the structures and element bonding in each species: 1. Carbon suboxide (C_3O_2): It is a linear molecule with only C=O double bonds present. 2. Pyrosulphate ion (S_2O_7^{2-}): It contains S-O bonds and an S-S bond. 3. Pyrophosphoric acid (H_4P_2O_7): It contains P-O bonds. 4. Dithionate ion (S_2O_6^{2-}): It contains S-O bonds and an S-S bond.

Step 2: Identify M-M Bond

Now, identify which species have a metal to metal-like bond (M-M) in addition to metal to oxygen (M-O) bonds: - Pyrosulphate ion (S_2O_7^{2-}) has an additional S-S bond. - Dithionate ion (S_2O_6^{2-}) also has an S-S (M-M like) bond. - Carbon suboxide and Pyrophosphoric acid do not have any M-M bonds.

Step 3: Conclusion

The species that have both M-M and M-O bonds are Pyrosulphate ion and Dithionate ion. In these compounds, the sulfur acts as the 'M' (metal-like element).

Key Concepts

Covalent Bonds

Covalent bonds are essential in chemistry and occur when two atoms share a pair of electrons. These bonds are pivotal because they allow atoms to fill their outer electron shells, achieving stability, similar to noble gases. Covalent bonding is prevalent in molecules consisting of nonmetals, where electronegativity differences between the atoms are not extreme. This type of bonding is more common in compounds like carbon suboxide and pyrosulphate ion. In the context of the given exercise, sulfur as an element can easily form covalent bonds with oxygen, leading to significant structural diversity. This characteristic allows sulfur to form double or single bonds, which are robust and play a major role in the stability and properties of these compounds.

Sulfur Compounds

Sulfur is a particularly interesting element in inorganic chemistry due to its ability to form a wide range of compounds. It can engage in a variety of bonding environments. In the pyrosulphate ion (\(S_2O_7^{2-}\)) and the dithionate ion (\(S_2O_6^{2-}\)), sulfur forms not only traditional S-O covalent bonds but also S-S bonds. These S-S bonds are significant because they exhibit characteristics similar to metal-metal bonding observed in some transition metals. Understanding sulfur's ability to bond with itself and with oxygen elucidates why these compounds exhibit such distinct chemical properties. The S-S bond confers a level of stabilization that enhances the sulfur compound's reactivity and stability.

Molecular Structure

The molecular structure of a compound determines its physical and chemical properties. This involves understanding not just which atoms are in the molecule, but how they are arranged. With molecules like pyrosulphate (\(S_2O_7^{2-}\)) and dithionate ions (\(S_2O_6^{2-}\)), the presence of both S-O and S-S bonds plays a crucial role in their structural configuration. This dual bonding setup creates a stable backbone, influencing how these compounds interact with other molecules.Analyzing molecular structures helps predict the behavior of compounds in various reactions. For instance, knowing that these structures have S-S bonds aides in understanding their potential to undergo oxidative or reductive processes more readily than those without such linkages.

Metal-like Bonding

Metal-like bonding is essentially the behavior of non-metal elements, such as sulfur, forming bonds that emulate characteristics typically seen in metal atoms. In the case of sulfur compounds like the pyrosulphate (\(S_2O_7^{2-}\)) and dithionate ions (\(S_2O_6^{2-}\)), the S-S bond can be likened to a "metallic" linkage. This is because sulfur, though a non-metal, can bond with itself in a way that resembles metal to metal bonding, contributing to the stability and unique properties of these ions.This "metal-like" property is what differentiates these compounds from others that solely exhibit non-metallic bonding characteristics, granting them greater structural integrity and reactivity potential.