Ionic and Covalent Bonds

What is Ionic Bond?

Def n ) Ionic Bonds are Bonds formed by transfer of electrons from one atom to another .

• Non Metals form ionic bonds with Metals .

• Non-metals gain electrons while metals lose electrons .
• Thus they form stable compounds .

Compounds formed between elements that have Ionic bonds are called Ionic Compounds.

Reaction of Sodium and Chlorine to form Sodium Chloride

Sodium

Sodium is a metal .

It has 1 valence electron . 

It needs to lose one electron in order to gain a stable electronic configuration.

Chlorine

Similarly, 

Chlorine is a non metal . 

It has 7 valence electrons . 

It needs to gain 1 electron to achieve stable configuration.

FORMATION OF NaCl:

When Sodium reacts with chlorine, it transfers its 1 outermost electron to the chlorine atom. By losing 1 electron, the sodium atom forms a sodium ion (Na ⁺ ) and by gaining 1 electron, the chlorine atom forms a chloride ion (Cl ^- ). This is shown below:

Reaction of Magnesium and Chlorine to form Magnesium Chloride

Magnesium  

We know that Magnesium is a metal and has 2 valence electrons.

Chlorine

Similarly, Chlorine is a non metal. It has 7 Electrons in outermost shell as shown below: 

Now to achieve inert gas configuration , Magnesium donates two of its electrons to two Chlorine atoms (one each) to form Magnesium Chloride as shown below:

When Magnesium reacts with chlorine, the magnesium atom transfers its two outermost electrons to two chlorine atoms. By losing 2 electrons, the magnesium atom forms a magnesium ion (Mg ²⁺ ) and by gaining 2 electrons, the two chlorine atoms form two chloride ions (2Cl ^- ). This is shown below:

Properties of Ionic Compounds

1. These are normally solid at room temperature.  
2. They are generally hard due to the strong forces of attraction between positive and negative ions. 
3. They have high melting and boiling points . 
   • This is because a large amount of energy is needed to break the intermolecular ionic bonds.
4. They are soluble in water . However,they are insoluble in organic solvents like kerosene and petrol. 
5. They do not conduct electricity in solid state. 
6. Since it is a rigid solid, there is a high force of attraction between oppositely charged ions . 
   • It is because of this, movement of electrons is not possible due to its rigid structure. 
7. However they conduct electricity in molten state. 
   • Heat is required to melt solid. The force of attraction between oppositely charged ions is overcome with the help of heat.
     • Hence they are able to conduct electricity and allow electrons to move .

Differences between Ionic and Covalent Compounds 

What are Covalent Bonds?

Def n ) Covalent Bonds are bonds formed by sharing of electrons between 2 atoms .

1. Formation of Hydrogen Molecule H 2

   • We know that the Atomic Number of Hydrogen is 1. This means there is one electron in the outermost  K shell. 

   • Thus, It needs to gain 1 electron to achieve inert gas configuration.

   • For this, it will share its electron with another Hydrogen atom to form Hydrogen compound.

   • Since it shares an electron, this type of bond is Covalent Bond .
     
     

2. Formation of Water Molecule H 2 O

Hydrogen

Atomic Number of Hydrogen is 1 meaning.

There is 1 valence electron in the outermost K shell. 

It needs to gain 2 electrons to achieve inert gas configuration.

Oxygen

We know that the Atomic Number of Oxygen is 16.

There are 6 valence electrons in the outermost M shell. 

It needs to gain 2 electrons to achieve inert gas configuration.

Formation of Water Molecule

We see that each of the two Hydrogen atoms share their electron each with one Oxygen atom.

Since electrons are shared, it is a covalent bond.

What are covalent compounds?

Compounds having covalent bonds are called covalent compounds .

Hence, the compounds formed by sharing of electrons are called covalent compounds.

Examples : H ₂ , H ₂ O.