Question

Highest covalent character is found in which of the following? (1) \(\mathrm{CaF}_{2}\) (2) \(\mathrm{CaCl}_{2}\) (3) \(\mathrm{CaI}_{2}\) (4) \(\mathrm{CaBr}_{2}\)

Short answer

(3) { highest uses character.

Step-by-step solution

Understand the Concept of Covalent Character

The covalent character of an ionic bond depends on the polarization power of the cation and the polarizability of the anion. According to Fajan's rules, smaller cations and larger anions lead to greater covalent character.

Compare the Cations and Anions

Comparing the compounds given:- All compounds have {2}^ + as the cation.- The size of the anions increases as follows: Attachment[4B] <= ' <= { <=I^.To. reduction[concept.{l))).s..anion.in.c 2]| type.Decreasingtrends :F^ + bond.

Identify the Compound with the Largest Anion

According to Fajan's rules, I^{2} IS gives highly character.

Key concepts

Fajan's Rules

Fajan's Rules help us understand the covalent character in ionic bonds. They describe the conditions under which an ionic bond takes on covalent properties. This covalent character increases when the cation has a high polarization power, and the anion is easily polarizable.

There are three main guidelines under Fajan’s rules:

• Size of the Cation: Smaller cations with high charge density distort the electron cloud of the anion more effectively.
• Size of the Anion: Larger anions with more diffuse electron clouds are more easily polarized.
• Charge on the Cation and Anion: Higher charges on either the cation or anion increase polarization.

These factors help determine which ionic compounds have significant covalent character. The distortion of the electron cloud in the anion due to the cation’s influence is crucial to understanding this concept.

Polarization Power

Polarization power refers to the ability of a cation to distort an anion’s electron cloud. The more a cation can distort the electron cloud, the greater the covalent character of the bond.

Several factors affect the polarization power of a cation:

• Size of the Cation: Smaller cations have higher polarization power because their positive charge is concentrated over a smaller area.
• Charge of the Cation: Cations with higher charges have greater polarization power because the increased charge exerts a stronger attractive force on the electrons of the anion.

An example is the comparison of a sodium ion, Na⁺, and a magnesium ion, Mg²⁺. The Mg²⁺ ion has a higher polarization power due to its smaller size and higher charge.

Anion Size

The size of the anion plays a significant role in determining the covalent character of an ionic bond. Larger anions are more easily polarized because their valence electrons are further from the nucleus and are more loosely held.

In the given exercise, we consider the following anions: F^-, Cl^-, Br^-, and I^-. The order of their size increases as follows:

• F^- (smallest)
• Cl^-
• Br^-
• I^- (largest)

According to Fajan's Rules, larger anions like I^- lead to greater covalent character.

This explains why in the exercise, CaI₂ is the compound with the highest covalent character among the given options.