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Group 1 elements
Concepts tested here
- Fajans' rules
All Questions
2009 AIPMT 1 question
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In the case of alkali metals, the covalent character decreases in the orderBy Fajans' rules, for a given cation the covalent character of an ionic compound increases with the polarisability of the anion.
The larger the anion, the more loosely its outer electrons are held and the more easily it is polarised (distorted) by the cation.
Size of halide ions: $F^- < Cl^- < Br^- < I^-$
So polarisability and covalent character increase in the order MF < MCl < MBr < MI.
Decreasing order of covalent character: MI > MBr > MCl > MF