Question

define 1) valence shell
2) valence
3) valency
4) valency of electrons

Answer 1

An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic cells or galvanic cells and the other ones are called electrolytic cells which are used to drive chemical reactions like electrolysis.[1][2] A common example of a galvanic cell is a standard 1.5 volt[3] cell meant for consumer use. A battery consists of one or more cells, connected either in parallel, series or series-and-parallel pattern.<r: A cell is a device which can convert chemical energy into electrical energy. A simple cell does this by using a combination of two metals (electrodes) and an electrolyte solution (which could be acid/alkali/salt solution). Metals can conduct electricity due to metallic bonding. Metallic bonds are the electrostatic force of attraction between negatively charged delocalised electrons and the positively charged metal ions. Metal atoms are surrounded by a “sea” of delocalised electrons. This means they are free to move within the structure- this gives metals its conducting abilities as an electric current can flow through it. A reaction between metals where electrons are gained is called a reduction reaction A reaction where electrons are lost is called a oxidation reaction A reaction where both reduction and oxidation occur is called a redox reaction. A redox reaction occurs when electrons are transferred from a substance that is oxidized to one that is being reduced.[4]

Electrolytic cellEdit
: Electrolytic cell



Nineteenth century electrolytic cell for producing oxyhydrogen.

An electrolytic cell is an electrochemical cell that drives a non-spontaneous redox reaction through the application of electrical energy. They are often used to decompose chemical compounds, in a process called electrolysis—the Greek word lysis means to break up.

Important examples of electrolysis are the decomposition of water into hydrogen and oxygen, and bauxite into aluminium and other chemicals. Electroplating (e.g. of copper, silver, nickel or chromium) is done using an electrolytic cell. Electrolysis is a technique that uses a direct electric current (DC).

An electrolytic cell has three component parts: an electrolyte and two electrodes (a cathode and an anode). The electrolyte is usually a solution of water or other solvents in which ions are dissolved. Molten salts such as sodium chloride are also electrolytes. When driven by an external voltage applied to the electrodes, the ions in the electrolyte are attracted to an electrode with the opposite charge, where charge-transferring (also called faradaic or redox) reactions can take place. Only with an external electrical potential (i.e. voltage) of correct polarity and sufficient magnitude can an electrolytic cell decompose a normally stable, or inert chemical compound in the solution. The electrical energy provided can produce a chemical reaction which would not occur spontaneously otherwise.

Answer 2

Valency.. Outer most orbit electron are present is called valency.
Valence.... If outer most orbit not present negative charge of electron is called valence.