Question

Which of the following is least ionic?
A) $AgCl$
B) $KCl$
C) $BaC{l}_2$
D) $CaC{l}_2$

Answer 1

Hint:Ionic compounds are formed by ions having opposite charge. They are a crystalline solid which are usually formed when metal reacts with non metals. They are held together by ionic bonds. The size of cation and anions helps in determining the structure of ionic compounds.


Complete Answer:
In this question, Fajan’s rule is used in which classification of certain compounds as ionic or covalent takes place.
There are some postulates of Fajan’s rule. Let us discuss these postulates:
Size of the ion: if a cation has smaller size and anion has larger size , then the covalent character of the ionic bond increases.
The charge of cation: ig the cation has greater charge then covalent character of ionic bond increases.
According to the postulates,
As we move left to right in a period, the size of the cation decreases and ionic character also decreases. Among $Ag,K,Ca,Ba$ , the compound that is present in the d block is $Ag$ whereas $K,Ca,Ba$ they are all present in s block.

Therefore, $AgCl$ is least ionic among the above options.


Additional informationIonic compounds show different properties. Let us discuss these properties:
1) Ionic compounds show high melting point and high boiling point because of the presence of electrostatic force of attraction between the ions which makes the bond so strong that high amount energy is required to break that bond.
2) Ionic compounds are soluble in polar solvent and insoluble in non polar solvent.
3) In solid state, ionic compounds don't conduct electricity because in solid state movement of ions does not take place and there will be no flow of charge from one point to another. In molten states, ionic compounds show electricity because the movement of ions takes place very easily.


Note:In this question we have discussed the Fajan’s rule that helps in finding the ionic tendency of the compound. Here, $AgCl$ shows least ionic character.
Elements have the tendency to gain and lose electrons to complete its octet and become stable and hence ions are formed.