The following acids have been arranged in the order of decreasing acid strength. Identify the correct order \(\mathrm{ClOH}\) (I), BrOH (II), IOH (III) (a) \(\mathrm{I}>\mathrm{II}>\mathrm{III}\) (b) \(\mathrm{II}>\mathrm{I}>\mathrm{III}\) (c) \(I I I>I I>I\) (d) \(\mathrm{I}>\mathrm{III}>\mathrm{II}\)

Understanding acid strength in halogens is crucial for grasping how their properties differ in various chemical reactions. In the case of halogen oxoacids, where the general formula is HXO, the 'X' represents a halogen such as chlorine (Cl), bromine (Br), or iodine (I). When we consider halogens, we often refer to their ability to donate a proton (H⁺) to form the corresponding anion. The ease with which a halogen acid can donate a proton is determined by the strength of the H-X bond. A weaker bond will result in the acid being stronger because it loses its proton more readily.

For halogen oxoacids, as we move down Group 17 from chlorine to iodine, the atoms get larger. This increase in atomic size leads to a longer bond length between the hydrogen and halogen atoms. A longer H-X bond is generally weaker, which means it breaks more easily to release a proton, thereby strengthening the acid. So, iodine, having the largest atom among the three, forms the weakest H-I bond, making IOH the strongest acid among the halogens addressed in the exercise.

Periodic trends are patterns observed within elements on the periodic table that show a predictable change when moving across periods or down groups. In Group 17, which is the group of halogens, there are several notable periodic trends, one of which directly relates to acid strength: atomic size. As you descend the group from fluorine to iodine, the atoms increase in size because each element has more energy levels. This larger atomic size leads to a greater distance between the nucleus and the valence electrons.

The larger the atom, the less tightly it holds onto its electrons, including the shared electron in the H-X bond. This decreased electronegativity as you go down the group means that the ability of the halogen to attract electron pairs is weaker, making the H-X bond less stable and more predisposed to donate its proton. Consequently, HI would be a stronger acid than HCl or HBr, following the atomic size trend in Group 17.

When comparing halogen acids like ClOH, BrOH, and IOH, we analyze their acid strengths to determine their reactivity and potential uses in chemistry. Acid strength can be influenced by factors such as the central halogen’s electronegativity, the stability of the resulting anion, and the bond strength and length.

In the exercise provided, considering the sizes of Cl, Br, and I, we have established that iodine forms the weakest bond with hydrogen, making IOH the strongest acid. This is followed by BrOH, with bromine being larger than chlorine but smaller than iodine, and therefore of intermediate acid strength. Finally, as chlorine is the smallest and most electronegative of the three, ClOH is the weakest acid. By summarizing these concepts, we can understand and predict the relative acid strengths of the halogen acids.