Arrange the following in order of decreasing ionic character.
a. `ClF_(3), SO_(2), N_(2), K_(2)O` and `LiF`
b. `Cl-H, F-H, Br-H, Na-I, K-F` and `Li-Cl`
c. `AlF_(3), AlCl_(3), AlBr_(3)`

Explanation

a. `overset(1+) (LiF) gt overset(1+) (K_(2)O) gt overset(4+) (SO_(2)) gt overset(3+)(C l F_(3)) gt overset(0)(N_(2))`
Apply Fajans' rule
(1) Low charge, (2) large cation and (3) small anion. More is the ionic character.
In `LiF` and `K_(2)O`, charge `(+1)` is same and size of `K^(o+) gt Li^(o+)`, but size of `F^(ɵ) lt "size of" O^(2-)`.
Hence, `LiF` is more ionic than `K_(2)O`.
ii. `overset(4+)(SO_(2)) gt overset(3+)(ClF_(3))`, Although charge on `ClF_(3)` is less than in `SO_(2)`. So, `ClF_(3)` should be more ionic than `SO_(2)`. But the order is reversed.
This is due to the size of `F^(ɵ) lt "size of" O^(2-)`.
b. `overset(1+)(K)-overset(1-)(F) gt overset(1+)(Li)- overset(1-)(Cl) gt overset(1+) (Na)-overset(1-)(I) gt overset(1-)(F) - overset(1+)(H) gt overset(1-)(Br) - overset(1+)(H) gt overset(1-)(C )-overset(1+)(H)`
Apply Fajans' rule
Charge `(+1)` on all the species is same.
In `KF` and `LiCl`, size of `K^(o+) gt` size of `Li^(o+)`, and size of `F^(ɵ) lt` size of `Cl^(ɵ)` .
In `LiCl` and `NaI`, although size of `Na^(o+) gt` size of `Li^(o+)` but size of `Cl^(ɵ) lt` size of `I^(ɵ)`.
In `NaI` and `F-H`, although size of `Na^(o+) gt` size of `H^(o+)` but size of `F^(ɵ) lt` size of `I^(ɵ)`.
In `overset(1-)(F)-overset(1)(H)` and `overset(1-)(Br)-overset(1+)(H)`, size of `F^(ɵ) lt` size `Br^(ɵ)`.
In `overset(1-)(F)-overset(1+)(H)` and `overset(1-)( C)-overset(1+)(H)`, size of `F^(ɵ) lt` size `C^(ɵ)`.

c. `overset(3+)(AlF_(3)) gt overset(3+)(AlCl_(3)) gt overset(3+)(AlBr_(3))`