chemistry

TYPES OF CONDUCTORS

(i)     Metallic or electronic conductors:

Conductors which transfer electric current by transfer of electrons, without transfer of any matter, are known as metallic or electronic conductors. Metals such as copper, silver, aluminum, etc., non-metals like carbon (graphite - an allotropic form of carbon) and various alloys belong to this class. These materials contain electrons which are relatively free to move. The passage of current though these materials has no observable effect other than a rise in their temperature.

(ii)   Electrolytic conductors:

Conductors like aqueous solutions of acids, bases and salts in which the flow of electric current is accompanied by chemical decomposition are known as electrolytic conductors. The substances whose aqueous solutions allow the passage of electric current and are chemically decomposed, are termed electrolytes.

The substances whose aqueous solutions do not conduct electric current are called non-electrolytes. Solutions of cane sugar, glycerine, alcohol, etc., are examples of non-electrolytes.

In order to pass the current through an electrolytic conductor (aqueous solution or fused electrolyte), two rods or plates (metallic conductors) are always needed which are connected with the terminals of a battery. These rods or plates are known as electrodes. The electrode through which the current enters the electrolytic solution is called the anode (positive electrode) with the electrode through which the current leaves the electrolytic solution is known as cathode (negative electrode). The electrolytic solution conductors electricity not by virtue of the electrolytic as in metallic conductors but as a result of movement of charged particles called ions towards the respective oppositely charged electrodes. The ions which carry positive charge and move towards cathode are termed cations while ions carrying negative charge which move towards anode are called anions. When these ions reach the boundary between a metallic and an electrolytic conductor, electrons are being either attached to or removed from the ions. Removal of electrons is termed oxidation (de-electronation) which occurs at anode while addition of electrons is called reduction (electronation) that takes place at cathode. Hence, flow of electrons through the outer circuit from anode to cathode across the boundary is accompanied by oxidation and reduction.