A branch of science that deals with the study of properties, composition and structure of materials, around us.

An element is a substance, which can neither be broken nor build from two or more simple substances.105 elements are known today.

A compound is a substance, which is made up of two or more elements, combined in fixed proportion by weight, and is decomposable into constituents through any method.

A mixture is obtained by mixing any two elements or compounds in any proportion. It may be homogenous or heterogeneous.

Structure of the atom

John Dalton put the theory that the all matter is made up of atoms. According to him; the atom is smallest particle of matter and may have independent existence. According to, modern atomic theory, an atom is made up of three particles protons, neutrons and electrons.

An atom is neutral, as the number of protons and electrons are the same.

The nucleus, is the central part of the atom, and is embedded with proton and neutrons. The electrons surround the nucleus, and lie in orbits & are in continuous motion.

The distribution of electrons in the orbits is called the electronic configuration.

The atomic weight equals the total number of protons & neutrons. The atomic number of atom equals the total number of electrons.

Periodic Table of Elements

D.I Mendeleev was the first person, which devised the periodic table of elements. According to him, elements can be arranged according to their atomic weight, and will show periodicity of the properties. All elements were arranged according to their atomic weights in horizontal and vertical columns.There are seven periods (horizontal columns) and 18 groups (vertical columns).The vertical columns were further subdivided into sub-groups, thus numbered 1A-7A, 1B-7B, 8 and O groups,

All properties of all elements in a one subgroup are same. According to Modern Periodic Table, all elements are arranged according to the atomic numbers, and groups & sub groups are alike with Mendeleev’s Periodic Table.

Some important elements and their uses

Hydrogen

Water is abundant in all chemical substances.It is very important for life, and all organic life have 50 to 70% of water.Water exists in all three kinds of matter solid, liquid and gas.Water is a universal solvent except a few substances. It has importance in agriculture, industry including chemical.A drinking water contains small amounts of different salts and gases.Rainwater is the purest form of the natural water.

Hydrogen has three types of isotopes

The Proteium isotope is the most abundant of all the hydrogen isotopes (up to 99.985%).

Heavy water (D2O) - is used as moderator in the nuclear reactors to slow down the fast moving neutrons. Hydrogen occurs in the nature in large amounts in water, acids, carbohydrates, plants and animals proteins, vitamins, wood, coal tar, oil & natural gas etc.

Hydrogenation is process, during which the vegetable oil in the presence of catalyst (nickel) is converted into vegetable ghee.

Hydrogen peroxide

Hydrogen peroxide is utilized in bleaching of wool and hair. In medicine, it is used as disinfectant. It is utilized in restoration of old parting in which lead oxide has been used as a white paint.

White lead in these paintings changes into black lead Sulphide on exposure to atmosphere. Hydrogen peroxide is used to oxidize black lead Sulphide to white lead Sulphate.

Hydrogen peroxide is used as a propellant for torpedoes. Concentrated hydrogen peroxide is now finding an important use as an oxidant for rocket fuel.

Water

• Water is the principal constituent 75% of earth’s surface and is an essential component of plants and animals in life processes.
• It constitutes about 65% of the human body and up to 95% of many plants.
• Water molecule is a bent molecule with a bond angle of 104.5.
• Water is a substance of great complexity.
• Water is a good solvent of ionic compounds but a poor one for covalent compounds.
• A number of ionic compounds like silver chloride, calcium fluoride, barium Sulphate and aluminium trifloride, are non soluble in water.
• Some carbon compounds such as alcohols, carboxylic acids and carbohydrates does not dissolve in water.

Soft and Hard Water

Soft water is either pure water (e.g. rain water), or soft water in which the dissolved impurities (e.g. sodium salts) do not hinder its lather forming property. Soft water forms rich lather with soaps immediately.

Hard water does not later with soaps immediately. IT is due to presence of some salts in water (mainly calcium and magnesium salts). Hard water is objectionable for many uses, particularly for washing, bathing or making steam in the industries. If hard water used in the industries. It leads to the formation of deposits in the boilers. A number of methods are generally employed for softening of water (i.e. converting the hard water into soft water). The hardness of water is of two types: -

Temporary hardness : It can be removed by boiling the water. It is due to the presence of bicarbonates of calcium or magnesium. On boiling, these bicarbonates decompose, and insoluble carbonates are removed by the filtration.It can also be removed by addition of a calculated amount of lime (calcium hydroxide)

Permanent hardness: It is due to presence of soluble calcium or magnesium salts (others than bicarbonates). From this type water hardness can be removed by precipitation (use of washing soda), by exchange of Ca, Mg ions with sodium ions in the zeolities. With use of calgon, the renders Ca & Mg ions ineffective.

Carbon and its compouds

• Carbon is the most abundant element on the earth. Carbon is most useful to the mankind, as it has served men with various ways-food material, fuels, cloths and drugs, which are made up of carbon compounds.
• Its various allotropic forms are diamond, graphite, coal, coke, etc. and each form is characterized by individual physical and chemical properties.
• Diamond is the most purest form of carbon, and are formed due to crystallization of carbon. The structure of diamond is a 3-D polymeric, in the form of tetrahedron, which makes the diamond one of the hardest material.
• Graphite is softest form of carbon, consists of sheets of carbon and which are atom, held together by vertical covalent bonds.

CO2 is present in the atmosphere with a concentration of 325 ppm. A natural equilibrium is maintained in level of CO2 in the atmosphere by photosynthesis & precipitation in form of carbonates, deposited as carbonate rocks and are it is also produced by combustion of organic matters.

In recent times concentration of CO2 has increased considerably after Industrial Revolution, and is one of cause for the greenhouse effect.

The carbon monoxide (CO) has very small amount in the atmosphere, and is produced during the combustion of oil in an automobile engine, or during when fuel is burned in a closed room.

CO is a colourless, odourless gas, and is a poisonous gas.

Its poisonous nature is due to the fact that combines with the haemoglobin of the blood, and forms indecomposable carboxy-haemoglobin, thus affecting oxygen carrying ability of the haemoglobin; this disorder is known as asphyxiation.

The carbon cycle maintains the level of CO2 in the environment, between production & consumption at a constant (0.04%) rate.

Nitrogen and its compounds

It is very essential for life; as it controls over-reactive oxygen in the air and in the form of protein & nucleic acid form a basis of life.

Ammonia is an important compound of nitrogen and is obtained commercially by the Haber’s process. Ammonia is used as a refrigerant, manufacture of fertilizers, medicines and others.

Nitrogen is an essential constituent of the plant and animal life. Animal gets nitrogen supply from plant and plants get it from the soil.

The nitrogen cycle maintains the nitrogen level in the environment. The blue green algae are adaptable enough to convert the atmospheric nitrogen into nitrogenous compounds.

Metals and their extraction

Metals are found in nature in the form of minerals or oreas. The native minerals are the metals occurring in a free state e.g. cooper, silver, gold etc. A mineral is composed of naturally occurring metals.

An ore is a mineral, from which metal can be extracted economically. Extration of a metal from an ore involves following steps.

i)      Beneficiation (concentration of the ore) in this process, ore is usually crushed and grounded until all the particles are broken down. The unwanted material (gangue) is removed using the washing, foam flotation process, magnetic separation, based upon difference between the ore and gangue.

ii)     Conversion of concentrated ore into simpler compounds- carbonated ores is converted into metal oxides by calcination and sulphide ores are converted into metal oxides by roasting.

iii)    Reduction of metal oxide: The metal oxides are reduced to meal by carbon, aluminum or electrolyte, reduction.

iv)    Refining of the impure metal: Refining is done to purify the metal, and is performed by electrolysis, liquation, distillation and oxidation methods

Alloy

Substance composed of two or more metals. Alloys, like pure metals, possess metallic luster and conduct heat and electricity well, although not generally as well as do the pure metals of which they are formed. Compounds that contain both a metal or metals and certain nonmetals, particularly those containing carbon, are also called alloys. The most important of these is steel. Simple carbon steels consist of about 0.5 percent manganese and up to 0.8 percent carbon, with the remaining material being iron.

An alloy may consist of an intermetallic compound, a solid solution, an intimate mixture of minute crystals of the constituent metallic elements, or any combination of solutions or mixtures of the foregoing. Intermetallic compounds, such as NaAu2, CuSn, and CuAl2, do not follow the ordinary rules of valency. They are generally hard and brittle; although they have not been important in the past where strength is required; many new developments have made such compounds increasingly important. Alloys consisting of solutions or mixtures of two metals generally have lower melting points than do the pure constituents. A mixture with a melting point lower than that of any other mixture of the same constituents is called a eutectic. The eutectoid, the solid-phase analog of the eutectic, frequently has better physical characteristics than do alloys of different proportions.

The properties of alloys are frequently far different from those of their constituent elements, and such properties as strength and corrosion resistance may be considerably greater for an alloy than for any of the separate metals. For this reason, alloys are more generally used than pure metals. Steel is stronger and harder than wrought iron, which is approximately pure iron, and is used, in far greater quantities. The alloy steels, mixtures of steel with such metals as chromium, manganese, molybdenum, nickel, tungsten, and vanadium, are stronger and harder than steel itself, and many of them are also more corrosion-resistant than iron or steel. An alloy can often be made to match a predetermined set of characteristics. An important case in which particular characteristics are necessary is the design of rockets, spacecraft, and supersonic aircraft. The materials used in these vehicles and their engines must be light in weight, very strong, and able to sustain very high temperatures. To withstand these high temperatures and reduce the overall weight, lightweight, high-strength alloys of aluminum, beryllium, and titanium have been developed. To resist the heat generated during reentry into the atmosphere of the earth, alloys containing heat-resistant metals such as tantalum, niobium, tungsten, cobalt, and nickel are being used in space vehicles.

Electrolysis

Electrolysis is a process whereby a compound commonly a salt is split into ions by the passge of electric current in a solution or molten state. The negative ions move towards the anode while the positive ions move towards the cathode.

It is of greater significance, since it had led to the development of important technical processes associated with the production and purification of non-ferrous metals and electro synthesis of organic compounds.

Electrolysis has found wide applications in industries and other fields.

The electrolysis is employed in the isolation of large number of metals (Na, Al, Mg, Ca, Cu, etc.) and non-metals (Cl2, F2, etc.). And manufacture of compounds such as sodium hydroxide, heavy water & potassium permanganate.

Electrodeposition of metals is also based on electrolysis.

Electrolytic decomposition is the basis for a number of important extractive and manufacturing processes in modern industry. Caustic soda, an important chemical in the manufacture of paper, rayon, and photographic film, is produced by the electrolysis of a solution of common salt in water (see Alkalies). The reaction produces chlorine and sodium. The sodium in turn reacts with the water in the cell to yield caustic soda. The chlorine evolved is used in pulp and paper manufacture.

An important industrial use of electrolysis is in the electrolytic furnace, which is employed in the manufacture of aluminum, magnesium, and sodium. In this furnace the resistance of a charge of metallic salts is used to heat the charge until it becomes molten and ionizes. The metal is then deposited electrolytically.

Electrolytic methods are also employed in the refining of lead, tin, copper, gold, and silver. The advantage of extracting or refining metals by electrolytic processes is that the deposited metal is of great purity. Electroplating, another industrial application of electrolytic deposition, is used to deposit films of precious metals on base metals and to deposit metals and alloys, as strengthening or wear-resistant coating, on metal parts. Recent advances in electrochemistry include the development of new techniques for placing layers of material on electrodes to increase their efficiency and endurance. Electrodes made out of polymers are now also possible, through the discovery of polymers that can conduct electricity.

Electroplating is done to provide inert and attractive coating on metals.

The metals most frequently used as plating materials are Cu, Ni, Cr, Zn and noble metals like silver and gold.

It is going to play an important role in future as a source of energy.