Carbon cannot reduce the oxides of sodium, magnesium and aluminium to their respective metals. Why? Where are these metals placed in the reactivity series? How are these metals obtained from their ores? Take an example to explain the process of extraction along with chemical equations.

Why Carbon Cannot Reduce Highly Reactive Metal Oxides

Carbon cannot reduce the oxides of sodium, magnesium, calcium, and aluminium to their respective metals because these metals have a much higher affinity for oxygen than carbon does. Carbon is a weaker reducing agent compared to these highly reactive metals and cannot break the strong ionic bonds between these metals and oxygen.

Position in the Reactivity Series

These metals (sodium, magnesium, calcium, and aluminium) are placed at the top of the reactivity series due to their highly electropositive nature and high reactivity.

Method of Extraction

These metals are obtained from their ores by electrolytic reduction of their molten oxides or chlorides. Since they are highly reactive, thermal reduction with carbon is ineffective, so electrical energy is used to reduce their cations.

Example: Extraction of Sodium from Molten Sodium Chloride

Sodium is extracted by the electrolysis of molten sodium chloride ($NaCl$).

• When electric current is passed through molten sodium chloride, the sodium ions ($Na^+$) migrate towards the cathode (negatively charged electrode) and get reduced to sodium metal.
• The chloride ions ($Cl^-$) migrate towards the anode (positively charged electrode) where they get oxidized to chlorine gas.

Chemical Equations:

• At Cathode (Reduction):

$$\text{Na}^+ + \text{e}^- \rightarrow \text{Na(s)}$$

• At Anode (Oxidation):

$$2\text{Cl}^- \rightarrow \text{Cl}_2\text{(g)} + 2\text{e}^-$$