Question

Indicate whether each of the following statements is true or false. For each statement that is false, correct the statement to make it true. (a) In general, the acidity of binary acids increases from left to right in a given row of the periodic table. (b) \(\mathrm{In}\) a series of acids that have the same central atom, acid strength increases with the number of hydrogen atoms bonded to the central atom. (c) Hydrotelluric acid \(\left(\mathrm{H}_{2} \mathrm{Te}\right)\) is a stronger acid than \(\mathrm{H}_{2} \mathrm{~S}\) because Te is more electronegative than \(\mathrm{S}\).

Short answer

(a) True. Acidity of binary acids generally increases from left to right in a given row of the periodic table due to increasing electronegativity. (b) False. Corrected statement: In a series of acids with the same central atom, acid strength generally increases with the increase in the electronegativity of the other atoms (usually oxygens) bonded to the central atom. (c) False. Corrected statement: Hydrotelluric acid (H2Te) is a stronger acid than H2S because Te is larger and has a lower electronegativity than S, making the bond between the hydrogen and tellurium atoms weaker, thus more easily releasing a hydrogen ion (proton).

Step-by-step solution

Statement (a)

The acidity of binary acids increases from left to right in a given row of the periodic table. This statement is true. As we move from left to right across a row of the periodic table, the electronegativity of the elements increases, leading to a stronger bond between the hydrogen atom and the non-metal, which results in an increase in acidity.

Statement (b)

In a series of acids with the same central atom, acid strength increases with the number of hydrogen atoms bonded to the central atom. This statement is false. To correct it, we can say: In a series of acids with the same central atom, acid strength generally increases with the increase in the electronegativity of the other atoms (usually oxygens) bonded to the central atom.

Statement (c)

Hydrotelluric acid (H2Te) is a stronger acid than H2S because Te is more electronegative than S. This statement is false. To correct it, we can say: Hydrotelluric acid (H2Te) is a stronger acid than H2S because Te is larger and has a lower electronegativity than S, making the bond between the hydrogen and tellurium atoms weaker, thus more easily releasing a hydrogen ion (proton).

Key concepts

Periodic table

The periodic table is a structured arrangement of chemical elements based on their atomic number, electron configuration, and recurring chemical properties. As we travel from left to right across a row in the periodic table, we encounter significant changes in electronegativity and atomic size. This organized pattern helps predict element behavior and chemical characteristics.

In terms of acid behavior, moving across a period often results in increased electronegativity of the elements. Higher electronegativity means a stronger attraction for electrons. Hence, this creates a stronger bond with hydrogen, increasing the acidity of binary acids formed with these elements. For example, in the same row, acids with more electronegative non-metals tend to be stronger.

Students often use the table to understand trends such as electronegativity and atomic size, which are pivotal in predicting acid strength, among other properties.

Electronegativity

Electronegativity is the tendency of an atom to attract shared electrons when forming a chemical bond. It varies across the periodic table and directly influences the behavior of acids and bases. Generally, electronegativity increases from left to right across a period, and decreases down a group.

When assessing acid strength, the electronegativity of the atoms involved is crucial. In binary acids, the more electronegative an element bonded to hydrogen, the more likely it will pull electron density away, thereby stabilizing the negative charge formed upon hydrogen ion release. This concept is why the statement about binary acids increasing in strength across a row is true.

• Higher electronegativity means stronger acids when moving left to right in a period.
• A lower electronegativity in the central atom can increase acid strength in other types of acids, due to weaker bonding allowing for easier hydrogen ion release.

Acid strength

Acid strength refers to an acid's ability to donate protons (hydrogen ions) in a solution. The stronger the acid, the more completely it dissociates in water.

Binary acids, such as hydrotelluric acid (H₂Te) and hydrogen sulfide (H₂S), demonstrate this well. Despite tellurium being larger and less electronegative than sulfur, H₂Te is a stronger acid due to weaker H-Te bonds compared to H-S bonds. Larger atoms create longer, weaker bonds, and easier release of hydrogen ions. This shows that in some cases, lower electronegativity, paired with larger atomic size, leads to stronger acids.

This contrasts with oxyacids where acid strength relates more to the electronegativity of the central atom and the number of oxygen atoms. More oxygen usually means more pull on electron density, thus stabilizing the negative charge more effectively. Each type of acid has its own distinct factors that contribute to strength, making understanding these differences crucial for chemistry students.