Question

Arrange the following in the increasing order of their covalent character.
\[ CaF_2;\; CaCl_2;\; CaBr_2;\; CaI_2 \]

• A. \( CaF_2 < CaI_2 < CaBr_2 < CaCl_2 \)
• B. \( CaF_2 < CaCl_2 < CaI_2 < CaBr_2 \)
• C. \( CaCl_2 < CaF_2 < CaBr_2 < CaI_2 \)
• D. \( CaF_2 < CaCl_2 < CaBr_2 < CaI_2 \)

Hint:

Larger anions are more polarizable and increase covalent characterAlways apply Fajan's rule in such questions.

Answer 1

The Correct Option is D

Step 1: Apply Fajan's rule.
According to Fajan's rule, covalent character increases with increase in polarization of the anion by the cation.
Polarization depends on size and charge of ions.

Step 2: Analyze cation.
In all compounds, the cation is same \( Ca^{2+} \).
Thus, polarization depends only on the anion.

Step 3: Compare halide ions.
Size of halide ions increases down the group:
\[ F^- < Cl^- < Br^- < I^- \]
Larger ions are more polarizable.

Step 4: Effect on covalent character.
Greater polarizability leads to higher covalent character.
Thus, covalent character increases in the order:
\[ F^- < Cl^- < Br^- < I^- \]

Step 5: Write order of compounds.
\[ CaF_2 < CaCl_2 < CaBr_2 < CaI_2 \]

Step 6: Conclusion.
Thus, increasing order of covalent character is:
\[ \boxed{CaF_2 < CaCl_2 < CaBr_2 < CaI_2} \]