Question

which compound has a more covalent character?

a. CdCl2 or CdI2

b. ZnO or ZnS

c. NaF or CaO

Answer 1

covalent character of compounds can explain better by applying Fajans rule.According to fajans rule "cation with smaller size and greater charge and anion with large size and less charge are more polarizing power and show more covalent character.that means the more covalent character is shown by smaller cation and larger anion.

in the above options

a.CdI₂ is more covalent than CdCl₂ because Iodine is larger in size than chlorine ion. and here cation is similar .so iCdI₂ will show more covalent nature .

b.ZnS is more covalent than ZnO.because in periodic tabnle going down the group size will increases,so here S>O .so S has larger size ,so anion withg large size show higher covalent character with similar cation .

c.here both choices cation and anions are different.so differnts in the electronegativity between cation and anion is helpful to find covalent nature of these compounds.the compound cation vs anion electronegativity difference in the range of zero to 0.4 is considered as covalent,0.5 to 1.7 is polar covalent and >>1.7 is ionic.

so in NaF difference in electronegativity is

the electronegativity of Na =0.9 and F=4 the difference is 3.1 so it is ionic in nature.

in CaO the electronegativity of Ca=1 and O=3.5, so difference is 2.5it is also ionic but it bis less ionic than NaF.So this shows CaO is comparatively covalent than NaF.