FARADAY’S EXPERIMENT: Passage of Electricity through solutions
Clue about Electrons:
We first consider the passage of electricity through chemical solutions called electrolytes. Earlier Davy had noticed that electric charges appear when solutions decompose by the passage of an electric current. Later this phenomenon was studied in greater details by Faraday.
Faraday observed that, when two metal plates called electrodes are placed in an electrolytic solution and an electric current is passed, the solution breaks up into charged particles called ions. There are positive ions and negative ions, depending upon the type of charge they carry. These ions travel to the oppositely charged electrodes, give up their charge and are liberated as neutral particles. He also determined the charges carried by different ions and also the amount of different elements liberated from the electrolytic solution when a given amount of charge passes through different electrolytic solutions.
What is of interest here, is that there is some elementary unit of electric charge associated with these ions which can be calculated. The ions were observed to carry some integral multiple of this charge. The basic unit of electric charge was later named by Stoney (1891), as “ELECTRON”.