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.

Na Atom - Teachoo.png



Chlorine

Similarly, 

Chlorine is a non metal

It has 7 valence electrons

It needs to gain 1 electron to achieve stable configuration.

Cl Atom - Teachoo.png

FORMATION OF NaCl:

Formation of Na+ ion Electron dot Structure - Teachoo.png

Formation of Cl- ion Electron dot Structure1 - Teachoo.png

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:

Formation of NaCl - Teachoo.png

Reaction of Magnesium and Chlorine to form Magnesium Chloride

Magnesium  

We know that Magnesium is a metal and has 2 valence electrons.
Mg atom - Teachoo.png

Chlorine

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

Cl Atom - Teachoo.png

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:

Formation of Mg2+ ion Electron dot Structure - Teachoo.png

Formation of Cl- ion Electron dot Structure - Teachoo.png

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:

Formation of MgCl2- Teachoo.png

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 .

Melting and Boiling Points of some Ionic compounds - Teachoo.png

Differences between Ionic and Covalent Compounds 

Ionic Compound

Covalent Compound

  1. Ionic Compounds are usually crystalline solids.
  1. Covalent compounds are usually liquids or gases. Only some of them are solids.
  1. Ionic Compounds have high melting points and boiling points. That is, ionic compounds are non-volatile.

2. Covalent compounds have usually low melting points and boiling points. That is, covalent compounds are usually volatile.

  1. Ionic Compounds conduct electricity when dissolved in water or melted.

3. Covalent Compounds do not conduct electricity.

  1. Ionic Compounds are usually soluble in water.

4. Covalent compounds are usually insoluble in water (except glucose, sugar urea, etc.)

  1. Ionic compounds are insoluble in organic solvents (like alcohol, ether, acetone, etc.).

5. Covalent compounds are soluble in organic solvents.

 

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 .
      Formation of Hydrogen Molecule - Teachoo.png

  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

Formation of Hydrogen Molecule1 - Teachoo.png

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.

 

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo