Which is the correct statement to explain that AgCl is more covalent than NaCl using Fajans rule
Answer
A. Smaller is the size of cation, greater is its polarization power
B. Cation with Pseudo inert gas configuration have higher polarization
c. AgCl is largely covalent while NaCl is largely ionic
D. All the above
The correct answer and explanation is:
The correct answer is D. All the above.
Fajan’s rule is used to predict the degree of covalent character in ionic compounds based on the polarization of ions. It suggests that the covalent character increases when there is a greater distortion or polarization of the electron cloud of the anion by the cation. The rule is based on several factors: the size and charge of the cation, the size and polarizability of the anion, and the electron configuration of the cation.
- Smaller is the size of cation, greater is its polarization power: This is the first key point in Fajan’s rule. A smaller cation has a higher charge density because its charge is concentrated in a smaller volume. This makes it more effective at polarizing the electron cloud of the anion, which leads to increased covalent character. In the case of AgCl (silver chloride), the Ag+ ion is relatively smaller than Na+ (sodium ion), leading to a stronger polarizing effect on the chloride ion.
- Cation with pseudo-inert gas configuration have higher polarization: The electron configuration of a cation also plays a significant role in its polarization power. Cations with a pseudo-inert gas configuration (like Ag+) are more polarizing because their outer electrons are more loosely held, which allows them to distort the anion’s electron cloud more easily. Ag+ has a configuration similar to that of the noble gas krypton (Kr), which increases its polarizing ability compared to Na+, which has a stable electron configuration resembling neon.
- AgCl is largely covalent while NaCl is largely ionic: Due to the smaller size and higher polarization of the Ag+ ion, AgCl exhibits more covalent character than NaCl. In NaCl, the larger Na+ ion results in less polarization of the chloride ion, keeping the bond predominantly ionic. The greater covalent nature of AgCl is also reflected in its lower solubility in water compared to NaCl, a property typically associated with covalent bonds.
In conclusion, the increased covalent character of AgCl compared to NaCl can be attributed to the smaller size of Ag+ and its pseudo-inert gas configuration, which make it a more effective polarizer of the chloride ion.