Question

Why do ionic compounds have a high melting point?

Answer 1

Hint: Ionic compounds are made up of cations and anions, bonded to each other via strong electrostatic force known as ionic bonding. In aqueous state they are good conductors of electricity.

Complete step by step answer:
-First let us see what an ionic compound and melting point is.
A compound which is composed of ions and these ions are held together by a type of electrostatic force known as ionic bonding, is known as an ionic compound. It is made up of positively charged ions known as cations and negatively charged ions known as anions, but overall charge of such compounds will be neutral (0).
For example: Sodium chloride (NaCl) is made up of $N{a^ + }$ and $C{l^ - }$ ions, ammonium carbonate is made up of ammonium ($NH_4^ + $) ions and carbonate ($CO_3^{ - 2}$) ions, etc.
The temperature at which the substance or compound changes its state from a solid to liquid is known as melting point.
-Now we will talk about why the ionic compounds have high melting points.
(1) In an ionic compound an equal number of cations and anions are arranged in a 3-D lattice because of which their melting point is high.
(2) The oppositely charged ions (the cations and anions) are attracted or bonded to each other by strong forces of attraction known as ionic bonding. Thus they have a high melting point.
(3) When an ionic compound is dissolved in water they dissociate into their respective cations and anions which act as charge carriers and conduct electricity. So, they are good conductors of electricity in aqueous state and also in molten state.
(4) The ionic bonding between the charged particle forms a giant structure of ions. Since the ionic bonding holding the giant structure is very strong, a large amount of energy will be required to break this bonding. Hence the ionic compounds have melting point and boiling points.
This is why ionic compounds have a high melting point.

Note: Ionic compounds are hard and brittle also. They are formed from their ions due to evaporation, freezing or precipitation. Mostly the metals form the cations and the non-metals form the anions. They are soluble in polar solvents. These ionic compounds can be acidic, basic or amphoteric.