Question

Potassium (at No. 19) and chlorine (at No. 17) form a compound. Explain the formation of the compound on the basis of :

(i) oxidation

(ii) reduction

(iii) oxidising agent

(iv) reducing agent

Answer 1

Potassium (K) and Chlorine (Cl) combine to form an electrovalent or an ionic compound.

• Ionic compound is formed by the complete transfer of electrons from the metal to the non-metal to gain the nearest noble gas configuration and complete the octet of electrons in the valence shell.
• Loss and gain of electrons lead to the formation of ions which combine to form an ionic bond.

As Atomic number= Number of electrons in a neutral atom

• Potassium has 19 electrons
• Electronic configuration of Potassium= 2, 8, 8, 1
• Chlorine has 17 electrons
• Electronic configuration of Chlorine= 2, 8, 7

(i) Oxidation: Oxidation is the process of loss of electrons form a species.

As Potassium is losing an electron to attain stability due to octet rule, therefore the process of loss of electron by Potassium is oxidation.

• Octet Rule: Octet rule states that the atoms that possess an octet of electrons (8 electrons) in the valence shell are stable than the ones that do not possess an octet of electrons.
  

$$\begin{gathered} \mathrm{K}\stackrel{\mathrm{Oxidation}}{\to }{\mathrm{K}}^{+}+{\mathrm{e}}^{-} \\ \left(\mathrm{Potassium}\right)(\mathrm{Potassium}\mathrm{ion}) \\ (2,8,8,1)(2,8,8) \end{gathered}$$

(ii) Reduction: Reduction is the process of gain of electrons by a species.

As Chlorine is gaining an electron to attain stability due to the octet rule, therefore the process of gain of electrons by Chlorine is reduction.

$$\begin{gathered} \mathrm{Cl}+{\mathrm{e}}^{-}\stackrel{\mathrm{Reduction}}{\to }{\mathrm{Cl}}^{-} \\ \left(\mathrm{Chlorine}\right)(\mathrm{Chloride}\mathrm{ion}) \\ (2,8,7)(2,8,8) \end{gathered}$$

(iii) Oxidising agent: The species which acts as itself gets reduced in the process of redox.

• As Chlorine is getting reduced by accepting electrons, therefore Chlorine is acting as an oxidising agent.

(iv) Reducing agent: The species that itself gets oxidised in the process of redox.

• As Potassium is getting oxidised, therefore Potassium is acting as a reducing agent.

Formation of Potassium chloride (KCl) occurs as follows:

• Potassium ion formed during the process of oxidation and Chloride ion are formed during the process of reduction as shown above.
• These ions are held together by the strong electrostatic forces of attraction as they are oppositely charged.
• This leads to the formation of Potassium chloride.