Question

State Fajan's Rules , And Give Suitable Examples.

Answer 1

Fajan's Rules

1. Fajan's rules are used in inorganic chemistry to predict whether a chemical bond will be covalent or ionic based on the charge on the cation and their relative sizes of cation and anion.
2. According to fajan's rules, the compounds will be ionic or covalent can be predicted on the basis of:

Ionic Bond	Covalent bond
The low positive charge on the cation	The high positive charge on the cation
The larger size of cation	The smaller size of cation
The smaller size of anion	Larger size of anion

3. Examples: among metal halides Lithium Iodide ($\mathrm{LiI}$) is most covalent due to larger size of anion (${\mathrm{I}}^{-}$) and Cesium fluoride is most ionic due to smaller size of anion (${\mathrm{F}}^{-}$).

Therefore, fajan's rules are used to predict whether a compound is ionic or covalent.