Question

How does the strength of an oxoacid depend on the electronegativity and oxidation number of the central atom?

Short answer

Oxoacid strength increases with higher electronegativity and oxidation state of the central atom.

Step-by-step solution

Understanding Oxoacid Components

An oxoacid consists of hydrogen, oxygen, and a central atom. The central atom influences the acid strength through its electronegativity and oxidation state.

Electronegativity's Role

The electronegativity of the central atom affects the oxoacid's strength. As the electronegativity increases, the molecule's ability to attract electrons strengthens, making the hydrogen more acidic due to a stronger pull from the central atom.

Oxidation Number's Role

The oxidation number of the central atom also affects oxoacid strength. Higher oxidation numbers increase acid strength because they attract electrons more strongly, weakening the O-H bond and making it easier to lose H⁺ ions.

Relating Factors to Acid Strength

Both high electronegativity and a high oxidation state lead to strong oxoacids. These factors enhance the electron-withdrawing ability of the central atom, leading to easier proton (H⁺) release and increasing acid strength.

Key concepts

Electronegativity

Electronegativity refers to the ability of an atom to attract electrons toward itself within a chemical bond. In the context of oxoacids, the central atom's electronegativity is crucial in determining the acid's strength. Consider that an oxoacid is composed of hydrogen, oxygen, and a central atom.
- If the central atom has high electronegativity, it pulls electrons towards itself more effectively. - This electron-attracting power weakens the bond between oxygen and hydrogen.When the O-H bond is weakened, it becomes easier for the molecule to lose a hydrogen ion (H⁺). As a result, the acid can release H⁺ more readily into the solution, increasing its acidity.
For instance, in the oxoacids of chlorine, such as hypochlorous acid (\( ext{HClO} \)), the electronegativity of chlorine influences its acidity. The more electronegative the central atom, the stronger the acid generally is.

Oxidation Number

The oxidation number of the central atom is another vital factor in determining oxoacid strength. The oxidation number is essentially the charge the atom would have if all bonds were ionic. It is an indicator of how many electrons the central atom can attract or share.
- As the oxidation number increases, the atom has a greater positive charge, which enhances its ability to attract electrons towards itself. - This, in turn, pulls electron density away from the O-H bond, weakening it.A weaker O-H bond means that the hydrogen ion (H⁺) can dissociate more easily, strengthening the acid. For instance, comparing sulfuric acid (\( ext{H}_2 ext{SO}_4 \)) and sulfurous acid (\( ext{H}_2 ext{SO}_3 \)), the higher oxidation state of sulfur in sulfuric acid contributes to its greater acidity.
Ultimately, a high oxidation number in the central atom often equates to a strong oxoacid.

Acid Strength

Acid strength refers to the tendency of an acid to donate protons, or hydrogen ions (\( ext{H}^+ \)), in a solution. For oxoacids, acid strength depends significantly on both the electronegativity and oxidation number of the central atom.
- High electronegativity in the central atom results in a strong pull on the bonded electrons, facilitating the dissociation of H⁺ ions.- A high oxidation number similarly enhances the electron-withdrawing capability of the central atom.Both properties lead to a more substantial ability of the oxoacid to release hydrogen ions, thereby demonstrating higher acid strength.
An example is perchloric acid (\( ext{HClO}_4 \)), a strong acid partly due to chlorine's high oxidation state and electronegativity, which together make the release of H⁺ very favorable.In summary, the stronger an oxoacid can pull electrons away from hydrogen, assisted by the factors mentioned, the stronger the acid will be.