What is the main distinction between ionic and covalent bonds? Explain with suitable examples.

What is the main distinction between ionic and covalent bonds? Explain your answer with suitable examples.

ANSWER :

Ionic Bond :

The bond formed by the complete transfer of electrons from one atom to another is called an ionic bond. Its also known as Electrovalent Bond.

Formation of NaCl

CONDITIONS FOR IONIC BOND:

 Following are the conditions that are necessary for the formation of ionic bonds.

  • One element should be metal while the other elements should be non–metal.
  • The electronegativity difference between two bonded atoms should be 1.7 or Above
  • The ionisation energy of metal should be low.
  • The ionisation energy of non-metal should be high

Bond Formation In NaCl :

  1. Sodium belongs to group 1A
  2. Chlorine belongs to group 7A
  3. The electronegativity of sodium is 0.9.
  4. While the electronegativity of chlorine is 3.0
  5. The electronegative difference between Sodium (Na) and chlorine (Cl) is 2.1
  6. Hence, an Ionic bond is formed
  7. Sodium (Na) has one electron in its valance shell.
  8. So, sodium (Na) loses one electron to form sodium ion (Na+) and attain the electronic configuration of (Neon)
  9.  Na -> Na + 1e
  10. Chlorine has seven electrons in its valance shell
  11. So it gains one electron to form chloride ions (Cl) and attain the electronic configuration of argon
  12.   Cl + 1e -> Cl
  13. The electrostatic force of attraction is established on Na+ and Cl-
  14. Therefore, crystal NaCl is formed.

    Na+ + Cl -> NaCl

Diagram Representation of NaCl

BOND FORMATION IN CALCIUM CHLORIDE

  • Ca belongs to group 2A
  • Cl belongs to group 7A
  • The electronegativity of calcium (Ca) is 1.0 ,while Chloride (Cl) is 3.0
  • The electronegativity difference  between Ca and Cl is 2.0
  • Thus, an Ionic bond is formed.
  • Calcium has 2 electrons in its outermost shell
  • It tends to lose the electrons and  attain the inert gas electronic configuration of Neon (Ne) and form Ca+2

    Ca -> Ca+2 + 2e-

  • Chlorine needs one electron to complete its outermost shell.
  • It tends to gain one electron to attain the nearest noble gas electronic configuration.
  • So it forms chloride ion (Cl-).
  • 2Cl+ 2e -> 2 Cl
  • Thus, the electrostatic force of attraction is established.
  • Hence, white-coloured crystalline CaCl2 is formed.

         Ca+2  + 2Cl -> CaCl2

Ionic bonding in CaCl2

COVALENT BOND:

The chemical bond formed by the mutual sharing of electrons between atoms is called a covalent bond.

Covalent bonding

CONDITIONS FOR COVALENT BOND:

Both the elements should be non-metals.

The electronegativity difference between two bonded atoms should be less than 1.7.

Example:

O2

N2

CH4

CO2

FORMATION OF CL2:

  • A chlorine molecule is formed from two chlorine atoms.
  • The chlorine atom electronic configuration is ( 2,8,7)
  • A chlorine atom has seven electrons in its valence shell.
  • The two chlorine atoms mutually share one electron to form a chlorine molecule (Cl2).
  • Therefore, both chlorine atoms attain the electronic configuration of argon(Ar) and complete their octet.

         Cl  +  Cl  -> Cl2

FORMATION OF CH4:

Carbon has four electrons in its valence shell and needs more 4 electrons to attain the noble gas (Ne) configuration.

Therefore, 4 atoms of hydrogen mutually share one electron each with a carbon atom to form a molecule of methane (CH4).

C + 4H -> CH4

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