Chemical Effects of Electric Current

Chemistry

Introduction

Atoms are the smallest units of matter, and they are combined together to form matter. Atoms contain charged particles. Atoms have a dense central region called the nucleus, which holds the neutrons (which are neutral) and protons (which have positive charge) . Electrons (negatively charged particles) orbit around the nucleus. As the electrons and the protons are equal in number, the atom is neutrally charged. Electrons are at varying distances from the nucleus. So the outermost electrons need the least force to be freed from an atom.  Metallic elements have these "free electrons" in the outermost layer. Electric current is set up when the "free electrons" move from one atom to another. 

Basic Terminology

Electric current: the flow of electrons from the negatively charged to the positively charged terminal in a closed circuit

Conventional current: The flow of electric current from the positively charged to the negatively charged terminal in a closed circuit.

Electric Conductors: Materials that allow electricity to pass through.

Electric Insulators: Materials that do not allow electricity to pass through. (also called poor conductors)

Electric conductivity: The ability of a material to conduct electricity.

Electrolyte: A liquid that can conduct electricity.

Ions: Charged Atom / Molecule

Cations: Positively charged ions

Anions: Negatively charged ions

Electric Conductivity of Liquids

A liquid contains cations and anions. The flow of these ions conducts electricity. The passage of current brings a chemical change in the liquid. (Example - Water breaks down to Hydrogen and Oxygen when electricity is passed.) Solutions of acids, bases, and salts have a large number of free ions to conduct electricity. 

Distilled or pure water does not conduct electricity, but water with impurities can. 

Electrolysis

When electricity is passed through the electrolyte, it initiates chemical reactions that split up the compounds of the electrolyte into the constituents. (for example, Water (H2O) will split into Hydrogen and Oxygen.) The process of splitting the electrolyte into its constituents is electrolysis. 

The 2 rods that help the current enters and leaves the electrolyte are called the electrodes. The anode and the cathode are the electrodes. The arrangement is called the electrolysis cell. 

Anode

The electrode at which the current enters.

The electrode where oxidation takes place. 

The electrode that attracts the anions. (*)

The electrode that is positively charged. 

Cathode

The electrode at which the current leaves.

The electrode where reduction takes place. 

The electrode that attracts the cations. (*)

The electrode that is negatively charged. 

Electrolysis of water

Electrolysis of water splits water into hydrogen and oxygen. As Hydrogen is a cation, bubbles of hydrogen gas are formed at the cathode. And as Oxygen is an anion, bubbles of oxygen gas form at the anode. It is because opposite charges attract (*).  Electrolysis of water forms twice as much hydrogen as oxygen as two Hydrogen molecules and one Oxygen molecule forms water. 

Electroplating

Electroplating is an application of electrolysis. It is the process of depositing a layer of the desired material on any other material. It is usually used as protection from corrosion and enhancing the appearance. 

The object to be coated is the cathode, while the material that will coat the object will be used as the anode. the salt solution of the anode is used as the electrolyte. 

The cations get attracted to the cathode, already covering one layer on the cathode. Next,
when electrons flow through, the electrons from the anode go to the cathode and deposit on the cathode because of the flow of the current.

For example: if a spoon is to be coated with copper, the cathode will be the spoon, the anode being the copper strip and the electrolyte being the copper sulphate. The copper ions from copper sulphate (being cations) will get attracted to the cathode, coating the cathode. Then the copper from the strip (anode) flows to the cathode, coating it completely. 

Tips

To remember what is the cation and the anion in a compound, remember the first is the cation, and the second is the anion. 

Examples:

H2O - Hydrogen is the cation, Oxygen is the anion

CuSO4 - Copper is the cation, Sulphate is the anion

NaCl - Sodium is the cation, Chlorine is the anion. 

The End.