Which compound from each of the following pairs ismore covalent and why ?
`{:((a),"CuO or CuS",(b),"AgCl or AgI"),((c ),PbCl_(2) or PbCl_(4),(d),BeCl_(2)or MgCl_(2)):}`

Explanation

This is explained with the help of Fazan's rules
(a) CuS is more colvlent than CuO because `S^(2)` ion is more polarised than the `O^(2-)` ion due to bigger size.
(b) AgI is more covalent than AgCl because `I^(-)` ion is more polarised than `Cl^(-)` ion due to bigger size.
(c ) `PbCl_(4)` is more covalent than `PbCl_(2)` because `Pb^(4+)` ion due to smallar size and grater magnitude of positive charge ismore polarising than `Pb^(2+)` ion.
(d) `BeCl_(2)` is more covalent than `MgCl_(2)` because the `Be^(2+)` ion is more polarising than `Mg^(2+)` ion dut to positive charge is more polarising than `Mg^(2+)` ion due to smaller size.