Which compound for each of the following pairs is more ionic and why ?
a. `BeBr_(2)` or `MgBr_(2)` , b. `PbCl_(2)` or `PbCl_(4)`
c. `AgBr` or `AgI` , d. `CuO` or `CuS`

Explanation

a. Appluy Fajans' rule :
A compound is more ionic if it has (i) large cation, (ii) small anion and (iii) low charge.
Size of `Mg^(2+) gt "Size of" Be^(2+)`
So, `MgBr_(2)` is more ionic.
b. `overset(2+)(Pb)Cl_(2)` is more ionic than `overset(4+)(Pb)Cl_(4)` because of low charge in `PbCl_(2)`.
c. `Ag Br` is more ionic than `AgI` (size of `Br^(ɵ) lt "size of" I^(ɵ)`).
d. `CuO` is more ionic than `CuS` (size of `O^(2-) lt "size of" O^(2-)`)