Question

Explain the formation of sodium chloride and calcium oxide on the basis of the concept of electron transfer from one atom to another atom.

Answer 1

Hint: The formation of an ionic bond is the result of an electrostatic force of attraction between charged ions which have acquired stability by completing their octet. Atoms lose their electrons so that their octet configuration can be completed.

Complete answer:

- Let us first discuss the formation of sodium chloride (NaCl).
- Sodium has eleven electrons which are arranged as 2 electrons in the first shell, 8 in the second and 1 in the outermost valence shell.

- Hence, its electronic configuration will be – (2,8,1).
- Chlorine has 17 electrons which are arranged as 2 electrons in the first shell, 8 in the second and 7 in the outermost valence shell.
- Hence, its electronic configuration will be – (2,8,7).
- As a result of the electronegativity difference, chlorine being the more electronegative atom has a tendency to extract the outermost electron of sodium thereby completing the octet (2,8,8) and becomes chloride ion ($C{{l}^{-}}$).
- Sodium which has lost an electron becomes sodium ion ($N{{a}^{+}}$) which also has completed its octet with the loss of one electron (2,8).
- Both the ions, being oppositely charged ions attract each other by means of electrostatic force of attraction to form NaCl molecules.

- Let us now discuss the formation of calcium oxide (CaO).
- Calcium has 20 electrons which are arranged as 2 electrons in the first shell, 8 in the second, 8 in the third and 2 in the outermost valence shell.
- Hence, its electronic configuration will be – (2,8,8,2).
- Oxygen has 8 electrons which are arranged as 2 electrons in the first shell and 6 in the outermost valence shell.
- Hence, its electronic configuration will be – (2,6).
- As a result of the electronegativity difference, oxygen which is more electronegative has a tendency to extract the 2 valence shell electron of calcium thereby completing the octet (2,8) and becomes an oxide ion (${{O}^{2-}}$ ).
- Calcium which has lost the two electrons becomes calcium ion ($C{{a}^{2+}}$) which also has completed its octet with the loss of 2 electrons (2,8,8)
- Both the ions being oppositely charged ions attract each other by means of electrostatic force of attraction to form CaO molecules.

- Hence, we have explained the formation of sodium chloride and calcium oxide on the basis of the concept of electron transfer from one atom to another atom.

Note: It is important to note that no compound is completely ionic in nature. There will be some percentage of covalent character in every ionic bond. And, there will also be some percentage of ionic character in every covalent bond.