What is ionisation? Please explain in easy language. Why does ionisation take place? How can covalent compounds be converted into ions as they are composed of molecules?

Ionisation: It is the process of formation of ions from ionic compounds.

For example NaCl

 

 

As you can see this process is reversible because they are bonded by the electrostatic force of attraction. hence they form ions on ionisation.

 

Let's move on to next question of dissociation of covalent compounds.

 

Let's take an example of HCl, 

HCl is formed by sharing the pair of electrons, but due to more electronegativity difference between H and Cl the bond becomes polar covalent bonds and the compound becomes the polar covalent compound.

 

Let's see its dissociation,

 

This happens because the OH^- ion from water molecule will attract the Cl^- ion of HCl hence as both are oppositely charged they attract towards each other and bond between H-Cl is broken and dissociates to form ions.