Question

Which one of the following order is correct regarding the covalent character of given molecules?

• A. \( \text{KF} > \text{KI} \)
• B. \( \text{SnCl}_2 > \text{SnCl}_4 \)
• C. \( \text{LiF} > \text{KF} \)
• D. \( \text{NaCl} > \text{CuCl} \)

Hint:

The covalent character of a molecule increases when the cation has a high charge density (small size, high charge), and when the anion is highly polarizable (larger size).

Answer 1

The Correct Option is C

- \( \text{KF}>\text{KI} \): \( \text{KF} \) has more covalent character than \( \text{KI} \) because F has a higher electronegativity than I, which makes the bond in \( \text{KF} \) more ionic, and less covalent.
- \( \text{SnCl}_2>\text{SnCl}_4 \): \( \text{SnCl}_2 \) has more covalent character than \( \text{SnCl}_4 \) because smaller ions (like \( \text{Sn}^{2+} \)) tend to polarize the chloride ions more than the larger \( \text{Sn}^{4+} \) ion, leading to more covalent character in \( \text{SnCl}_2 \).
- \( \text{LiF}>\text{KF} \): This is correct because lithium has a small ionic radius and high charge density, which allows it to polarize the fluoride ion more than potassium in \( \text{KF} \). This leads to a higher covalent character in \( \text{LiF} \).
- \( \text{NaCl}>\text{CuCl} \): This is incorrect as \( \text{CuCl} \) has more covalent character due to the polarizing effect of the small \( \text{Cu}^+ \) ion.
Thus, the correct answer is \( \text{LiF}>\text{KF} \).