Why ionic bond is non directional but covalent bond is directional?

Why ionic bond is non directional but covalent bond is directional?

Actually, there is no existence of ionic bond. Ionic bond is nothing but a force of electrostatic attraction between cationand anion, which is formed by the lose or gain of electrons.

Since there is no direction of electrostatic attraction force, so ionic bond or ionic valency has no specific direction.

On the other hand, a covalent bond is formed  by the overlapping  of two orbital. Since each orbital have its own direction, so covalent bond or covalency must have  also a direction .

For example, in ammonia molecule, three sp3 hybridized orbital of ‘N’- atom overlap  with the ‘s'- orbital of hydrogen atom and the desired compound is NH_3.

Now, it has been found  that the H – N –H  bond angle is about same with the bond  angle among the sp3 hybridized orbital.

Consequently, we can say that ionic bond or ionic valency is non directional and covalent bond or covalency is directional.  

Why are ionic bonds not called a real bond?

A covalent bond is formed between two atom by sharing of electrons. So, there is a real existence of covalent bond  and it has a particular direction.

But, ionic bond is nothing but electrostatic force of attraction between cation and  anion which formed by lose or gain of electrons . 

There is no pair of electron is present between cation and anion and also force of attraction has no direction .

Hence, ionic bond is not called a real bond. 

What is the driving force for ionization of an acid in aqueous solution?

The ionization of an acid molecule in aqueous solution is as follows,

In aqueous solution of an acid, the lone pair on oxygen atom of water molecule form co-ordinate bond with H⁺ ion. As a result, hydroxonium ion ( H₃O⁺ ) is obtained.  

Due to formation of this co-ordinate bond, the octet of ‘O’-atom  remain unchanged but hydrogen atom  gain the electronic configuration like helium atom.

Besides this, the hydroxonium ion ( H₃O⁺ ) have three equivalent canonical structure ,through which it gains stability.
  

When this stable hydroxonium ion ( H₃O⁺ ) is formed, at that time a specific amount of hydration energy ( 256 Kcal / mol  ) is released. This energy is used to separate or interrupt H⁺ ion from acid molecule.

Therefore, the tendency of H⁺ ion to form stable hydroxonium ion  ( H₃O⁺ ) with water molecule in aqueous solution, is the source of driving force of ionization of an acid molecule.

Summary

Why  ionic bond  is non directional but covalent bond is directional ?

Why are ionic bonds not called a real bond ?

What is the driving force for ionization of an acid in aqueous solution?

What is Ulmann reaction ? Click here.