Properties of Ionic and Covalent Compounds

In this universe, there are three types of compounds found – Ionic compounds, Covalent compounds and Coordinate compounds. Out of these three, the most prevalent ones are the ionic and covalent compounds. Ionic compounds are formed between two elements by transfer of one or more electrons between them and thus one becoming positively charged cation and another negatively charged anion. On the other hand, covalent compounds are those compounds that are formed by the mutual sharing of two elements. Now, after understanding the basic definition of both these compounds, let’s now look at their properties as:

What is an Ionic Compound?

When two atoms have a substantial difference in electronegativity, ionic bonding develops. This significant difference causes the less electronegative atom to lose an electron and the more electronegative atom to receive that electron, resulting in two ions. An ionic bond is formed when two oppositely charged ions are attracted to one other via electrostatic attraction. When a non-metal function as an electron acceptor and metal acts as an electron donor, ionic bonding occurs. 

Because metals have few valence electrons while nonmetals have closer to eight, the nonmetal will take an electron supplied by the metal to easily meet the octet rule. In an ionic connection, more than one electron can be supplied and received.

NaCl, KI, and MgCl₂ are examples of ionic bonding chemicals.

Properties of Ionic Compounds

1. Ionic compounds are made of oppositely charged ions and are hard solid in the state. This is because they have a very strong electrostatic force of attraction between them thus, they are tightly packed and cannot be easily separated.
2. Ionic compounds have high melting and boiling points because ionic compounds are comprised of oppositely charged ions which attract each other thus, there is a strong electrostatic force of attraction between them, so a large amount of energy is needed to break the bonds and thus, they have high melting and boiling points.
3. Ionic compounds do not conduct electricity in the solid-state. This is because the electrostatic force of attraction between the ions in the solid-state is very high. Thus, there are no free mobile electrons present in the compound in solid so these compounds do not conduct electricity in solid-state.
4. Ionic compounds conduct electricity when they are infused state and are in aqueous solutions. This is because of the presence of free mobile ions in the fused state as the electrostatic force of attraction between these ions weakens infused state. On the other hand, when these compounds are dissolved into water, water being a polar covalent compound decreases the electrostatic force of attraction and thus resulting in the presence of free mobile ions in an aqueous solution.
5. Ionic compounds are highly soluble in water while they are not soluble in organic solvents like toluene.
6. Ionic compounds are good electrolytes as they can easily pass electricity through their aqueous solutions. The particles of the ionic compounds dissociate into ions and are discharged into separate particles at both the electrodes (i.e the cations get discharged at the cathode and the anions get discharged at the anode).
7. The speed of chemical equations is very fast. Since they can form ions in an aqueous solution very easily. Thus, it can form new compounds very easily.

Now, having understood the properties of ionic compounds let’s now understand c the properties of covalent compounds:

Properties of Covalent compounds

1. Covalent compounds consist of molecules and they can exist in all three states of matter (solid, liquid or gas). This is because they are made up of molecules and thus the force of attraction between these molecules are weak and so they exist in all three states of matter.
2. The melting and boiling points of covalent compounds are usually low. This is because they are made up of molecules that are held together by the weak force of attraction thus less heat is required to break the force of attraction between these molecules and so they have low melting and boiling points.
3. They are mostly non-conductor of electricity. This is because they are comprised of molecules, and, due to the absence of free mobile ions in these compounds electricity can not pass through them.
4. Non-polar covalent compounds do not ionize when dissolved into the water but polar covalent compounds. But polar covalent compounds like Hydrogen chloride, Ammonia etc. forms ions when dissolved into water and acts as electrolytes.
5. Covalent compounds do not have ions in them. Thus, they do not dissociate into ions.
6. Covalent compounds are not soluble in water but they are soluble in organic solvents like toluene. But this is the case with non-polar covalent compounds, polar covalent compounds are soluble in water.
7. The speed of reaction of covalent compounds are very slow as compared to the ionic compounds. Since covalent compounds are comprised of molecules, so in covalent compounds, old bonds are broken and new bonds are formed while forming new compounds during the chemical reactions, thus, they are slower than the ionic compounds.

Now let’s discuss some questions based on the properties of ionic and covalent compounds.

Sample Questions

Question 1: Ionic compounds are hard solids. Explain.

Answer:

Ionic compounds are made up of ions (positively charged cations and negatively charged anions) and thus, there is a strong electrostatic force of attraction between these ions and so they are hard solids.

Question 2. Covalent compounds are usually not bad conductors of electricity. Why it is so?

Answer:

Conduction of electric current through any substance requires the availability of free mobile ions. On the other hand, covalent compounds are entirely made up of molecules and thus, there are no ions present in them. Thus, due to the non-availability of free ions in the covalent compounds, they are bad conductors of electricity.

Question 3. Discuss the difference between the ionic and covalent compounds with respect to the boiling and melting point of the compound.

Answer: 

Electrovalent or ionic compounds have a high boiling and melting point whereas covalent compounds have a low melting and boiling point. This is because ionic compounds are made up of ions which are held together by the strong electrostatic force of attraction between them and it requires a lot of energy to break them whereas covalent compounds are made up of molecules and thus, it takes much lesser energy to break these bonds.

Question 4. What are polar covalent compounds? Name two polar covalent compounds.

Answer:

Polar covalent compounds are those compounds that are formed by polar covalent bonds. Polar covalent bonds are the covalent bonds which are asymmetric and there is an unequal sharing of electrons between the atoms.  

Some examples of polar covalent compounds are Water (H₂O), Hydrogen Chloride (HCl), etc.

Question 5: What is do you mean by the term dissociation of ions?

Answer:

Dissociation of ions in the process of separation of an ionic compound into its constituent ions(cations and anions). 

e.g.

• NaCl dissociates into Na⁺ and Cl^–.
• KCl dissociates into K⁺ and Cl^– ions.

Question 6: What do you mean by the term ionization?

Answer:

Ionization is the process in which an atom or the molecule changes into an ion (cation or anion) by gaining or losing electrons. Polar covalent compounds ionize when they are dissolved into ions.

Question 7: Compare potassium chloride and Carbon tetrachloride with respect to solubility.

Answer:

Potassium chloride being an electrovalent compound is highly soluble in water but it is not soluble in organic solvents like toluene while carbon tetrachloride being a covalent compound is not soluble in water but is highly soluble in organic solvents like toluene.