Give the decreasing order of covalent character of the following compounds.
a. I. `GeCl_(2)` II. `GeCl_(4)` III. `SnCl_(2)` IV. `SnCl_(4)`
V. `PbCl_(2)` VI. `PbCl_(4)`
b. I. `CH_(4)` II. `NH_(3)` III. `H_(2)O` IV. HF
c. I. HF II. HCl III. HBr IV. HI
d. I. AgI II. NaI III. CuI IV. NaCl

Explanation

a. First chech the charge, gigher the charge on the ions, more is the convalent character (since anion is same)
I. `overset(+2)(Ge) Cl_(2)` II. `overset(+4)(Ge) Cl_(4)` III. `overset(+2)(Sn) Cl_(2)`
IV. `overset(+4)(Sn) Cl_(4)` V. `overset(+2)(Pb) Cl_(2)` VI. `overset(+4)(Pb) Cl_(4)`
So, group compounds of higher charges appear first and then come the lower charges. All the compounds belong to group 14. Now check the size of the cation, the small cation shows more covalent character.
Hence the decreasing order of covalent character is
`(underset("Size increases and +4 charge")overset(overset(4+)(Ge Cl_(4)) overset(4+)(Sn Cl_(4)) overset(4+)(Pb Cl_(4)))(rarr) rangle underset("Size increased and +2 charge")overset(overset(2+)(Ge Cl_(2)) overset(2+)(Sn Cl_(2))overset(2+)(Pb Cl_(2)))(rarr))`
i.e. `(II gt IV gt VI gt I gt III gt V)`
b. Check the charges on the ions. Higher the chatge on the ions, more is the covalent character.
So, the decreasing order of covalent character is
`underset("decreasing charges on the ions")overset(overset(+4-4)(CH_(4)) gt overset(+3 -2)(NH_(3))gtoverset(+1xx2-2)(H_(2)O)gt overset(o+ ɵ)(HF))to` (I gt II gt III gt IV)
c. Since charges on the ions (cation and anion) are same and cation `(H^(o+) "ion")` is also same. So, check the size of anion.
Large anion, more is the covalent character (all anions of group 17).
So, the decreasing order of convalent character is
`HI gt HBr gt HCl gt HF (IV gt III gt II gt I)`
d. Charges on the ions are same.
Size of `Cu^(o+)~~` Size of `Na^(o+)`
Moreover, `Ag^(o+)` and `Cu^(o+)` have d configuration.
Size of `Ag^(o+) gt` Size of `Cu^(o+)`
Small cation, with d configuration is more covalent. Large anion with d configuration is more covalent.
So, the decreasing order of covalent character is
`Cu I gt Ag I gt Na I gt NaCl (III gt I gt II gt IV)`