Basic Concepts of Chemistry

1.     Basic Concepts of Chemistry.
Chemistry is the branch of science which deals with the study of matter, its physical and chemical properties, the physical and chemical changes which it undergoes and the energy changes that accompany these processes.
Matter : Matter is anything that has mass and occupies space.
It can be changed from one form to another or into energy but can never be completely destroyed.
Elements of Chemistry
An element is a substance which can neither be broken nor built from two or more simple substances by any physical or chemical method.
Or in other words an element is a pure substance which contains only one kind of atom, e.g., Fe (Iron), Na (Sodium) etc.
Types of Chemistry Elements
  • Metals
  • Non – Metals
  • Metalloids
Compounds of Chemistry
A compound is a pure substance which contains more than one kind of element or atom in fixed proportion by weight e.g., NaCl (Sodium chloride), SO2 (Sulphur dioxide), etc.
Types of Chemistry Compounds
  • Organic Compounds
  • Inorganic Compounds
The properties of a compound are completely different from those of its constituents.
Mixtures in Chemistry
A material containing two or more elements or compounds in any proportion is a mixture. It can be separated into its constituents, e.g., Air, Milk, Paints, Cements etc.
Types of Mixtures in Chemistry
Homogeneous : A mixture is said to be homogeneous if its composition is uniform throughout.
Heterogeneous : A mixture is said to be heterogeneous if its composition is not uniform.
The properties of a mixture are the properties of its constituents. A mixture with definite boiling point is known as azeotropic mixture.

Separation of Mixtures in Chemistry
  • Sublimation : In this process, a solid substance passes directly into its vapours on application of heat, and when vapours are cooled, they give back the original substance, e.g., iodine, napthalene, benzoic acid etc.
  • Sedimentation and Decantation : This method is used when one component is liquid and the other is insoluble solid.
  • Crystallization : This method is based on the difference in solubility of the various compounds in a solvent, e.g., mixture of KNO3 and NaCl can be separated by this process.
  • Filtration : It is used for quick and complete removal of solid suspended particles from a liquid (or gas) by passing the suspension through a filter.
  • Evaporation : In this method the solution is heated so that the solvent vaporises to give the solute (solid substance) e.g., salt can be obtained from salt solution.
  • Distillation : A mixture of two substances, only one of which is volatile, can be separated by this process, e.g., NaCl can be separated from water by distillation.
  • Fractional Distillation : This process is used if both the components of a mixture are volatile. It is based on the difference of boiling points, e.g., the various fractions of crude petroleum can be separated by this process.
  • Steam distillation : It is used to separate a liquid (should be immiscible with water) from a mixture by heating with steam, e.g., lemon oil, toluene, nitrobenzene etc.
  • Mechanical Separation : Two immiscible liquids can be separated by using a separatory funnel e.g., oil and water.
  • Magnetic Separation : Two solids one of which is magnetic substance can be separated by this method.
  • Atmolysis : In this process a mixture of gases can be separated based on their rates of diffusion, e.g., Isotopes of uranium (U235 and U238) are separated by converting them into gaseous UF6.
  • Chromatography : This is the most versatile separation method which can be applied to solid, liquid or gas. In this method the components of a mixture are adsorbed on a suitable adsorbent at different rates and thus get separated, e.g., to separate coloured materials from dyes, green vegetables, ink etc.
2.     Atomic Structure of an Element.
Atomic Structure
In 1809, Dalton suggested that atom is the smallest particle of the element and it is indivisible.
But in the beginning of 20th century Rutherford, J.J. Thomson etc. suggested that atom is divisible and made up of electrically charged particles.
The electron is a fundamental particle of an atom which carries a unit negative charge.
It was discovered by J.J. Thomson in 1897.
It is a fundamental particle of an atom carrying a unit positive charge.
It was discovered by Rutherford and Goldstein in 1886.
It is a fundamental particle of an atom carrying no charge.
It was discovered by Chadwick in 1932.
Charge and Mass of Fundamental Sub – Atomic Particles
Discovered by
9.10939 x 10-31
e, -1e 0
J.J. Thomson
1.672 x 10-27
p, 1H¹
16.74793 x 10-27
n, 1n¹
Properties of Cathode Rays
  • They travel in straight lines
  • They cast shadow of solid objects placed in their path.
  • They cause mechanical motion i.e., they consists of material particles.
  • They carry -ive charge.
  • These rays are deflected when magnetic field is applied on them.
  • They produce heating effect.
  • They cause ionization of gas through which they pass.
  • They produce green fluorescence on the glass walls of the discharge, tube as well as on certain other substances such as zinc suplhide.
  • They effect the photographic plates.
  • They have penetrating power.
  • The ratio of charge / mass (i.e., e / m) = 1.76 x 108 coulombs / g.
Properties of Anode Rays
  • They travel in straight lines, however, their speed in much less than that of cathode rays.
  • They are made up of material particles.
  • They are positively charged.
  • They deflect in electric and magnetic field.
  • The ratio of charge / mass is found to be different for the particles constituting anode rays when different gases are taken inside the discharge tube.
Properties of Nucleus
  • Nucleus of an atom consists of protons and neutrons which are collectively known as nucleons.
  • The forces that bind the electrons to the nucleus are electrical or coulombic in nature.
  • Density of nucleus is enormous and is of order of 1014 g/cm.
  • Instability of the nucleus is due to high neutron proton ratio.
  • The radius of the nucleus is around 5 x 10-13 cm (5 Fermi).
Atomic Number (Z)
Atomic number of an Element. = Total No. of protons present in the nucleus = Total No. of Electrons present outside the nucleus. (or) Z = p = e
Mass Number (A)
Mass Number = Number of Protons + Number of Neutrons
A = p + n (or) A = z + n
Mass Number =>A
Atomic Number =>ZX
e.g., 2311Na, 1735Cl and so on
3. Alloys in Chemistry.
Cu (60 to 80%), Zn (40 to 20%)
For making household utensils
Cu (75 to 90%), Sn (25 to 10%)
For making coins, idols, utensils
German Silver
Cu (60%), Zn (25%), Ni (15%)
For making utensils
Mg (5%), Al (95%)
For making aircraft frame
Rolled Gold
Cu (90%), Ni (10%)
For making cheap ornaments
Monel metal
Cu (70%), Ni (30%)
For making alkali resistant containers
Bell metal
Cu (80%), Sn (20%)
For making bells
Gun metal
Cu (85%), Zn (10%), Sn (5%)
Used for engineering purposes
Sn (50-75%), Pb (50-25%)
Soldering of metals
Al (95%), Cu (4%), Mg (0.5%), Mn (0.5%)
In aircraft manufacturing
Fe (98%), C (2%)
For making nails, screws, bridges
Stainless Steel
Fe (82%) Cr, Ni (18%)
For making cooking utensils, knives
An alloy is a mixture of two or more metals.

4.     Cement
Portland Cement
The approximate composition of Portland Cement is :
  • Calcium Oxide → 62%
  • Silica → 22%
  • Alumina → 7.5%
  • Magnesia → 2.5%
  • Ferric Oxide → 2.5%
The above compounds are provided by the two raw materials :
  • Lime Stone
  • Clay
In cement almost entire amount of lime is present in combined state as calcium silicates and calcium aluminates.
Note :
  • Cement containing excess amount of lime cracks during setting while cement containing less amount of lime is weak in strength. Setting of cement is an exothermic process.
  • A small amount of gypsum is added to slow down the setting of cement.
  • Cement with excess of silica shows slow setting and that having an excess of alumina shows quick setting.
  • Cement containing no iron is white but hard to burn.
  • It is a mixture of cement, sand, gravel (small pieces of stones) and approximate amount of water.
  • When the cement concrete is filled in and around a wire – netting or skeleton of iron rods and allowed to set the resulting structure is known as “Reinforced – Concrete”.

5.     Chemical Bonding in Chemistry
Mainly 3 Types of bonds can be present in Chemical Compounds.
I. Electrovalent or Ionic Bond
It is formed by Transferring of Electrons between 2 Atoms.
These types of bonds are mainly formed between Metals and Non – Metals.
Properties of Ionic Compounds
  • These compounds have high B.P., M.P. and thermal stability.
  • These compounds give fast reactions since, ionic reactions are spontaneous.
  • These compounds exist in solid form.
II. Covalent Bond
It is formed by equal sharing of Electrons between 2 Atoms. This type of bond is mainly formed between non – metals.

6.     Chemical Reactions and their Results.
If a lighted paper is introduced in a jar of carbon dioxide?
The flame will be extinguished because carbon dioxide does not help in burning.
Blue litmus is put into a solution of acid?
It turns red.
Red litmus is put into a solution of base / alkali why?
It turns blue.
Why does a candle blow off when covered?
Because it does not get oxygen which helps in burning.
Why is phosphorous kept in water?
Because with air it catches fire and in water it is insoluble.
Sugar gets charred on heating. Why?
When sugar is heated above 200°C decomposes into carbon and water and therefore gets charred.
If flame water is kept in air?
If turns milky due to carbon dioxide in the air.

Why does the mass of an iron rod increase on rusting?
Because rust is hydrated ferric oxide (Fe2O3 . 3H2O) which adds to its mass.
Why is salt mixed with ice when making ice cream?
Salt causes reduction of temperature and helps to freeze the cream and freezing temperature is lowered from 0°C to 5°C
Why does milk curdle?
Lactose (milk sugar) content of milk undergoes fermentation and changes into lactic acid which on reacting with lactose forms curd.
Why does milk turn sour?
The microbes react with milk and grow. They turn lactose into lactic acid which is sour in taste.
Why doesn't hard water lather soap profusely?
Hard water contains sulphates and chlorides of magnesium and calcium which from an insoluble compound with soap. Therefore soap does not lather
with hard water.
Why does sea water boil at a higher temperature than fresh water?
Sea water contains impurities which raises the boiling point of water.
Why is it dangerous to have charcoal fire burning in a closed room?
When characoal burns its produces carbon monoxide which is suffocating.
Why is dangerous to sleep under trees at night?
Plants respire at night and give out carbon dioxide which reduces the oxygen content of air required for breathing.
Why does ENO's salt effervesce on addition of water?
It contains tartaric acid and sodium bicarbonate. On adding water carbon dioxide produced which when released into water causes effervescence.
7. Chemical Changes in Chemistry
(i) Combination Reactions : Combination reactions occur when two substances unite to form a third substance.
For example, combining magnesium (Mg) and oxygen (O2) result in the production of magnesium oxide (MgO)
2Mg + O2=> 2MgO
This ereaction can be accomplished by burning magnesium in air, which supplied the oxygen.
(ii) Decomposition Reaction : Decomposition reaction occurs when a single compound breaks down into two or more simpler substances.
In the decomposition of mercuric oxide (HgO), the elements mercury (Hg) and oxygen (O2) are produced.
2HgO=> 2Hg + O2
(iii) Displacement Reaction : When one element replaces another in a compound, it is known as a displacement reaction.
For example, iron (Fe) may displace copper (Cu) in a solution of cupric sulphate (CuSO4).
Fe + CuSO4=> FeSO4 + Cu
(iv) Double Decomposition Reactions : When two compounds interact to form two other compounds, it is known as a double decomposition reaction.
For example, Sodium iodide (Nal) and lead nitrate (Pb(NO3)2) react to form lead iodide (Pbl2) and sodium nitrate (2NaNO3).
2NaI + Pb(NO3)2=> Pbl2 + 2NaNO3
(v) Hydrolysis : Hydrolysis is a double decomposition reaction in which water reacts with a second substance.
When ammonium chloride (NH4Cl) is combined with water (H2O), it undergoes hydrolysis, yielding ammonium hydroxide (NH4OH) and hydrochloric acid (HCl).
NH4Cl + H2O=> NH4OH + HCl
(vi) Neutralization Reactions : Neutralization is the interaction of an acid with an equivalent quantity of a base.
If the process is carried out in an aqueous solution (dissolved in water), the products are water and a salt.
For example, hydrochloric acid (HCl) and sodium hydroxide (NaOH) neutralize each other when dissolved in water, forming sodium chloride (NaCl), a salt, and water (H2O).
HCl + NaOH -> NaCl + H2O
(vii) Substitution Reaction : Substitution reactions occur when an element, such as chlorine (Cl), replaces one or more hydrogen atoms in a hydrocarbon, such as methane (CH4).
CH4 + Cl2=> CH3Cl + HCl
8.     Common and Chemicals Names of Some Compounds.
Common Name
Chemical Name
Chemical Formula
Dry Ice
Solid Carbon dioxide
Slaked Lime
Calcium Hydroxide
Ca (OH)2
Bleaching Powder
Calcium Oxychloride
Ammonium Chloride
Caustic Soda
Sodium Hydroxide
Rock Salt
Sodium Chloride
Caustic Potash
Potassium Hydroxide
Potash Alum
Potassium Aluminium Sulphate
K2SO4 . Al2(SO4)3 . 24H2O
Magnesium Sulphate
MgSO4 . 7H2O
Quick Lime
Calcium Oxide
Plaster of Paris
Calcium Sulphate
(CaSO4) ½ H2O
Common Name
Chemical Name
Chemical Formula
Calcium Sulphate
CaSO4 . 2H2O
Green Vitriol
Ferrous Sulphate
FeSO4 . 7H2O
Mohr's Salt
Ammonium Ferrous Sulphate
FeSO4(NH4)2SO4 . 6H2O
Blue Vitriol
Copper Sulphate
CuSO4 . 5H2O
White Vitriol
Zinc Sulphate
ZnSO4 . 7H2O
Marsh Gas
Acetic Acid
Potash Ash
Potassium Carbonate
Sodium Thiosulphate
Na2S2O3 . 5H2O
Baking Powder
Sodium Bicarbonate
Washing Soda
Sodium Carbonate
Na2CO3 . 10H2O
Magnesium Oxide
Chalk (Marble)
Calcium Carbonate
Lunar Caustic
Silver Nitrate
Laughing Gas
Nitrous Oxide
Tricholoro Methane
Mercuric Sulphide
Na2B4O7 . 10H2O
Ethyl Alcohol
Heavy Water
Duterium Oxide
Globar's Salt
Sodium Sulphate
Na2SO2 . 10H2O
Tri Nitro - toluene
Mercurous Chloride
Silicon Oxide

9.     Different Forms of Carbon Allotropy
A phenomenon in which an element is found in different forms having different physical properties but similar chemical properties is known as allotropy.
The different forms are called the allotropic or simply allotropes.
Phosphorus, sulphur, carbon etc. are elements which occur in different allotropic forms.
It has various allotropic forms but these can be classified into crystalline form (diamond, graphite) and amorphous form (coke, coal, lamp – soot, carbon black, animal charcoal, gas carbon, wood charcoal etc).
Crystalline forms of Carbon
1. Diamond : Diamond is the purest form of carbon. It is found very deep inside the earth, in South Africa, Congo, Angola.
Of late, synthetic diamonds have also been prepared.
  • It is the hardest natural substance.
  • It is insoluble in any solvent
  • It is of specific gravity 3.5
  • It is non – conductor of Heat and Electricity.
  • It burns in air at 900°C and gives out CO2.
  • It occurs as octahedral crystals
  • It is transparent and has refractive index of 2.45.
  • It occurs in Free State.

  • It is used in making jewellery
  • It is used for cutting hand tools
  • For drawing thin wires, diamond dies are used.
2. Graphite : Also called as black lead. As compared to diamond, it is widely available in nature in countries like India, Sri Lanka, Canada, Russia etc.
It can also be produced artificially by heating anthracite coal with little iron oxide of silica in electric furnace.
  • It is soft.
  • Its specific gravity is 2.3.
  • It is good conductor of heat and electricity
  • It is black in colour
  • It is insoluble in ordinary solvents
  • It burns in air at 700 – 800°C and gives out CO2.
  • It is of hexagonal crystals.
  • It is used in writing pencils and lead.
  • It is used as a lubricant for high temperature.
  • It is used as refractory material for designing crucibles and electrodes for high temperature.
  • It is used in electro – typing and manufacturing of gramophone records for making the non – conducting surface as conducting.
Amorphous Forms of Carbon
3. Coal : Its common variety is bituminous which is like hard stone and burns with smoky flame.
The superior quality coal burns without smoke and is called anthracite.
It is formed out of carbonization of organic and fossil matter buried deep into the earth, under high pressure and high temperature with very – very limited supply of air, during centuries. Anthracite, Bituminous, Lignite and Peat are the types of coal with decreasing C%.
  • It is used as a fuel.
  • It is used in the manufacturing of coal gas. The by – products of this process are coke, coal – tar, ammonical liquor. Coal – tar is a source for making dyes, explosives, chemicals etc.
  • It is also used in manufacturing fuel gases like producer gas, water gas and semi – water gas.
  • It is used for manufacturing of synthetic petrol by catalytic hydrogenation of coal.
4. Coke : It is a coal deprived of volatile constituents such as coal gas, ammonia, benzene, phenol, tar etc.
It is manufactured from coal by destructive distillation by heating in the absence of air due to which volatile constituents are left back in the coal.
  • It is used as a fuel.
  • It is used for making graphite and water gas.
  • It is used as reducing agent in iron and steel industry.
5. Wood Charcoal : When wood is suitably stocked, encased in an earthy / clay cover and ignited with a very limited supply of air, the volatile products are allowed to escape, and wood charcoal is obtained.
  • It is used as a fuel.
  • It is used a constituent of gun – powder.
  • It is used for purification of water.
  • It is used as a deodorant and decolourising agent in sugar solution and gas masks.
6.Bone Black or Animal Charcoal : When bones are subjected to destructive distillation in a retort, the residue obtained is boneblack or animal charcoal.
7.Lampblack : When tar or vegetable oil rich in carbon is burnt in an insufficient supply of air, black soot is deposited on the wet blankets hung in the room.
  • It is used in making Indian ink.
  • It is used in making printers ink.
  • It is also used by ladies for eyelids decoration.
8. Carbon Black : It is obtained by burning natural gas in the presence of limited supply of air and collecting the soot on the underside of a revolving disc which is scrapped off and packed.
  • It is used in the rubber for making automobile tyres.
  • It is used as a replacement of lamp black used for many a purpose.
9. Gas Carbon and Petroleum Coke : Gas carbon is produced by scrapping the carbon from the walls of the retort formed as a result of destructive distillation of coal.
When distillation of crude petroleum is done in a retort, the petroleum coke is deposited on the walls of the retort.

  • It is used for making electrodes when pressed into sticks, as both are good conductors of electricity.
10. Sugar Charcoal : It is the poorest form of carbon.
  • It is obtained when sugar is heated strongly out of contact with air.
  • It can be liquefied even to room temperature but under high pressure.
Further, it can be converted into a solid state, known as dry ice which is used as a mobile refrigerant.
11. Carbon – 14 : It is a useful radioactive isotope for tracer studies in organic and biochemical system, including the determination of the age of materials that were once alive.
The identity and amount of many elements present in trace amounts in mixtures may be determined by neutron activation analysis.
This procedure involves the conversion of non – radioactive isotopes of chemical elements and the determination of the type and intensity of the radioactivity that results.
10.                         Dyes in Chemistry
Coloured substances used for colouring Textiles, Foodstuffs, Silk, Wool, etc., are called dyes.
But all coloured substances are not Dyes. For a substance to act as a dye, it must fulfill the following requirements.
It must have a suitable attractive colour, i.e., it should absorb light in the visible Region. It must be able to fix itself to the fabrics by either Physical or Chemical Bonding.
It must be fast to light; it must not be affected either by water, dilute acids or alkalies.
Different classes of dyes are discussed below.
Nitro Dyes : These are polynitro derivatives of phenol where nitro group acts as a chromophore and hydroxyl group as auxochrome.
These are less important industrially because the colours are not fast.
Azo Dyes : These are an important class of dyes and are characterized by the presence of azo group (-N = N-) as the chromophore.
The groups like NH2, NR2 or -OH etc, present in the molecule containing one or more azo groups act, as the auxochromes.
Triphenyimethane Dyes : These dyes contain the paraquinoid moiety as chromophore and -OH,-NH2 or -NR2 as auxochrome.
These dyes are not fast to light and washing and hence are mainly used for colouring paper or typewriter ribbons, e.g., malachite green which is used for dyeing wool and silk directly and cotton after mordanting with tannin.
Direct dyes: These include dyes which can be directly applied to the fabric when the latter is dipped in a hot aqueous solution of the dye.
Wool and silk are dyed by direct dyes.
The polar groups of the fabric (proteinic structure) unit with the polar groups of the dye and thus the dye is chemically fired upon the fibre.
Example of direct dyes are Mautius yellow, Naptho yellow S, Congo red, etc.
Mordant Dyes : Those dyes which are fixed on the fibre with the help of a modrant are known as mordant dyes.
Various mordants depending upon the nature of the dye are used.
For acidic dyes, basic mordants (such as hydroxides of iron, aluminium and chrornium) are used, while for basic dyes, acidic mordants (like tannic acid) are used.
Here the fabric is first dipped into a solution of mordant and then into the dye solution.
The colour produced depends on the nature of the mordants used.
Using alizarin as Mordant dye and aluminium, chromium and iron as mordants, red, brownish – red tones and black – violet colours, respectively are produced.
Vat Dyes : These are water insoluble dyes and are introduced into the fibre in its soluble) reduced form, also known as leuco form (colourless).
The parent dye is regenerated by oxidant with air or a suitable chemical.
These are called vat dyes because reducing operation (using sodium hydrosulphite) was formerly carried out in wooden vats.
Indigo is a vat dye and is used for Dyeing Cotton.
11.                         Electrolysis in Chemistry
Electrolysis Process of decomposition of an electrolyte (a compound formed by electrovalent bonds) by the passage of an electric current through its molten state or its aqueous solution is called electrolysis and the experimental arrangement used for this purpose is called an electrolytic cell.
Applications of Electrolysis
The process of electrolysis is applied in a number of fields for various purposes.
Some of the important applications are discussed below :
(i) Electroplating :
It is a process of depositing one metal (generally a superior metal such as silver, gold, nickel or chromium) over another metal (which is generally a basal metal, such as iron or copper) through the process of electrolysis Electroplating may be carried out for preservation of decoration.
For example, articles made of iron are electroplated with tin, nickel or chromium to prevent rusting, similarly, many household articles such as tea sets and decoration pieces made of metals like copper and brass are electro plated with gold or silver to enhance their beauty.
(ii) Electrorefining :
Metals can be refined (purified) by the electrolytic method. A thick slab of impure metal is made the anode and a thin sheet of pure metal is made the cathode in the solution of a suitable salt of the metal to be purified.

On passing electricity, the anode goes on dissolving and the pure metal gets deposited at the cathode.
The impurities are thrown down in the form of anode mud Copper is industrially purified by this method.
(iii) Electro – Printing :
In large – scale printing, impression of the ordinary type page is made on wax of plaster of Paris.
The wax plate is made a conductor by sprinkling graphite on it and then made cathode in copper plating bath.
On passing electric current, copper deposits on the wax plate till a sufficient thickness of copper deposits is obtained.
It is removed and strengthened by filling its back with type – metal. The mould obtained is an exact copy of the printer’s page and is used in large scale printing.
(iv) Electro – Metallurgy :
The process of extraction of metal from its ore by electrolysis is called electrometallurgy.
For example, sodium is obtained by electrolysis of fused sodium chloride; while aluminium is extracted by the electrolysis of bauxite is fused cryolite.
(v) Industrial Preparations :
A large number of chemicals used in industry and medicine are prepared electrolytically.
For example, caustic soda, washing soda, chlorine, and so on are obtained by electrolysis of sodium chloride, while hydrogen and oxygen are manufactured by electrolysis of acidulated water.

12.                         Elements Symbols and Atomic Numbers
Atomic No
Atomic No
Iron (Ferum)
Copper (Cuprum)
Sodium (Natrium)
Tin (Stannum)
Atomic No
Atomic No
Antimony (Stabnium)
Gold (Aurum)
Mercury (Hydragerm)
Lead (Plumbum)
Potassium (Kalium)
13. Glass in Chemistry.

Ordinary glass is solid mixture of silica (SiO2), sodium silicate (Na2SiO3) and calcium silicate (CaSiO3).
Glass is a super cooled liquid hence; it has no definite crystal structure and melting point.
But the average composition of glass is x . M2O . yM’O . 6SiO2, where M is a monovalent alkali metal like Na, K etc., M’ is a bivalent metal like Ca, Pb, Zn etc. and x and y are whole numbers.
Thus, ordinary glass may be represented as Na2O . CaO . 6SiO2.
Hence we can say that glass is a mixture, not a compound.
Annealing of Glass
The process of slowly cooling of glass in annealing kiln is called Annealing of glass.
Types of Glass
Glass is of following Types :
1. Soft – Glass :
It is sodalime silicate glass (Na2O . CaO . 6SiO2).
It melts at low temperature It is used in manufacturing of bottles, test tubes and glass of windows etc.
2. Hard – Glass :
It is potash lime silicate (K2O . CaO . 6SiO2).
It melts at high temperature in comparison to soft glass and is used in manufacturing of flask, etc.
3. Flint – Glass :
It is lead – potash silicate (K2O . PbO . 6SiO2) and is used in manufacturing of prism and lens of optical instruments.
4. Crookes – Glass :
It is special type of optical glass containing circum oxide which cut off ultra violet rays harmful to eyes and used in manufacturing of lens of spectales.
5. Pyrex – Glass :
It is a mixture of sodium aluminum borosilicates (Na2O . Al2O3 [B2(SiO3)3]). Its coefficient of expansion is very low and hence it can withstand sudden temp changes.
It has high percentage of silica, about 80%. It is used in manufacture of high quality equipments in laboratory because it does not melt at very high temperature.
6. Quartz – Glass :
It is obtained from pure silica. It has a low coefficient of expansion and does not break even when plunged in water while red hot.
7. Ground Glass : It is prepared by grinding ordinary sand (soft) glass by emery and turpentine oil.
8. Reinforced Glass : It has a network of wires embedded in and does not shatter easily.
9. Safety – Glass :

It is also known as Shatter Proof glass. It is prepared by placing a layer of transparent plastic glass (usually a sheet of vinyl acetate resin) between two layers of glass by means of a suitable adhesive.
This glass does not break easily under ordinary impact. It is used in making wind screen of automobiles, aero – planes, trains etc.

14. Important Elements and Compounds
It is Colourless, Odourless, Tasteless, Inflammable and Lightest known substance (gas).
It is found in water (H2O), in organic compounds and all living things. It is neutral to litmus.
Can be produced in the laboratory by Bosch process and by electrolysis. It is used m balloons, ships, for ammonia and vanaspati ghee preparation etc.
It is Colourless, Tasteless, Odourless, Combustible Slightly Heavier than Air, some what soluble in Water. Atmospheric Air contains Oxygen by about 21% by Weight.
It can be prepared in the laboratory but also in factories on Commercial Scale.
It can be liquefied and solidified. It is employed in welding process and also used in hospitals for artificial respiration.
It is colourless, tasteless, odourless, non – combustible, in – active, non – poisonous gas, forming about 80% of the atmospheric air by volume and 75% by weight.
It is slightly lighter than air and only slightly soluble in water. It is used for filling electric bulbs, for making fertilizers, ammonia, nitrates etc.
It is an allotropic form of oxygen containing three atoms in the molecule and is formed when oxygen or air is subjected to silent electric charge.
It is bluish gas, very active chemically and a powerful oxidizing agent. It is found in the upper atmosphere some 25 to 30 km from the earth’s surface, called ozonosphere layer.
It is this layer which absorbs a large proportion of the sun’s ultraviolet radiation. Ozone is used for purifying air and water and in bleaching.
It is universal constituent of living matter. It can be mainly classified into two forms :
Allotropic form and amorphous form.
Diamond and graphite are two of its allotropic forms whereas charcoal, lamp black, coke etc., belong to amorphous form. Carbon atoms are capable of uniting with each other to form very large molecules upon which life is based.
It is a very costly stone and hardest naturally occurring substance. It is transparent to X – Rays only. It is used for jewellery, drilling and cutting tools. It can be cut only by a diamond.

Graphite :
It is soft, easily powdered and gives a greasy feeling. It is good conductor of heat and electricity.
Used for lead pencils, electrical machines and as lubricant for heavy machines. Also used as a moderator in nuclear reactors.
Over long periods of time, trees, bones get buried under the ground by violent geological changes. As a result of chemical reaction with clay, sand, water etc. these get transformed to coal in nature.
This process is known as carbonization. Due to this process we get substances like peat, lignite, bituminous (soft) and anthracite (hard) depending upon degree of carbonization.
Organic compounds
Constitute substances like petroleum, coal, food components (protein, fats carbohydrates, vitamins), anaesthetics, antiseptic, antibiotics, cotton, wool, silk synthetic fibres.
These are compounds of hydrogen and carbon vizard methane, ethane, propane, butane benzene. Hydrocarbons are found abundantly in nature viz., petroleum, natural gas coal etc.
From these natural hydrocarbons or parent organic compounds many other organic compounds can be derived.
It is a hydrocarbon compound extracted from the ground or sea bed by deep drilling, Petroleum is then refined in distilleries and converted into petroleum products such as petrol, diesel, grease, lubricating oil.
The residue of this is used for making man – made fibre like nylon, terylene, plastic etc., and wide range of drugs.
Natural gas, CNG are another range of products of hydrocarbon compounds.
Noble Gases
Noble gases are gaseous elements and are also known as rare gases as these are of low amount in the atmosphere.
They are called noble gases because of their chemical inertness.
The noble gases are: helium, neon, argon, krypton, xenon and radon.
Radon, of course, is not present in the atmosphere. However, it is produced in the radioactive decay of radium.
Helium is present in sun’s atmosphere as well as in natural gas up to maximum of 10%.
Noble gases are colourless and odourless and are exclusively used as inert atmosphere in welding and cutting, inside electric bulbs and in metallurgical operation.
In liquefied form, the natural gases are used for creating low temperature.
Halogens are the four elements fluorine, chlorine, bromine and iodine.
Fluorine and chlorine are gases, bromine is a violatile liquid and iodine is a volatile solid.
Halogens are highly reactive.
They do not occur in nature in Free State but only as compounds.
Their colours are :
  • Fluorine – Pale yellow
  • Chlorine – Yellowish green
  • Bromine – Reddish brown or Orange
  • Iodine – Violet black
It is widely used in drinking water supply as germicide.
It is also used for manufacturing bleaching powder, disinfectants, hydrochloric acid and many organic compounds.

It is a non – metallic element. It burns with a blue flame emitting sulphur dioxide.
It occurs in many allotropic forms, as the elements in many volcanic regions and as sulphides of many metals.
It is employed in vulcanizing rubber, manufacturing of dyes and chemicals in medicines and for killing moulds as well as pests.
It is necessary for life. It too occurs in many allotropic forms, mainly as calcium phosphate.
White phosphorus is very inflammable and poisonous solid. Its compounds are employed as fertilizers and detergents.
It is a non – metal, found abundantly in earth’s crust and sand and in rocks as silica or silicates.
Semi – Conductors are made of pure elements of silicon. As silicates, it is widely used for manufacturing glass. It is also used in alloys.

Bases soluble in water are called alkalies viz. sodium hydroxide and potassium hydroxide.
They have a soapy touch, bitter taste and turn red litmus blue and yellow turmeric powder (Haldi) brown.
Its main ore is pitchblende. It is a radioactive metal, occurring in nature, comprising of 99.28% (92238U) and 71% (92235U).
The isotope (92238U) has the capacity of sustaining a nuclear chain reaction and is used in nuclear reactors and nuclear weapons.
It is a dark grey radio active metal used in alloys and as a source of nuclear energy. Its compounds occur in monozite and thorite
It is a transuranic element (element having atomic number more than 92) which do not occur in nature but may be obtained by nuclear reaction. It is radio active.
The isotope (94239Pu) is produced in nuclear reactors and is of great importance as it undergoes nuclear fission when bombarded by slow neutrons. This isotope is employed in nuclear weapons.
It is extracted from its ores by the blast furnace process.Iron obtained from blast furnace is called pig iron or cast iron containing about 5% carbon. Pure iron is called wrought iron which does not contain carbon more than 0.2%, or any other impurities or constituents. Wrought iron is soft, malleable, easy to work on. It is used for making chains, wires, furniture, items of decoration and electromagnets.
It is a metal element, malleable, ductile and best conductor of electricity after silver.
It is widely used for making electrical wires and in steam boilers being not affected by water or steam.
It is used for alloying e.g., bronze, brass, gun metal, German silver, bell metal, Dutch metal etc.
It is a metal element, bluish white in colour. It occurs as calamine, zincite and zinc blende.
It is used for alloying e.g., brass and in galvanizing iron.
It is a metal element, light white in colour, occurring widely in nature in clays, extracted mainly from ore: bauxite.
It is ductile, malleable, can be drawn into wire, widely used in electric transmission and distribution, being a good conductor of electricity.
It is quite light. It is also used as an alloy.
Alloyed aluminium is extensively used in manufacturing utensils, electrical apparatus, automobile engines, pistons and also in aircrafts.
It is a metal element, soft, white malleable, best conductor of electricity.
It is used in jewellery and coins. Its compounds are used in photography.
It is a metal element, bright yellow, soft, malleable, non – corrodible by air and unaffected by most acids, but dissolves in aqua regia.
It is alloyed with silver and copper. It is the best conductor of electricity but is not used being very costly.
Gold, particularly in India is extensively used for jewellery and dentistry.
Its compounds are employed in photography and medicines. It is also used for surface plating.
It is a metal used extensively in the form of various salts which are further used as fertilizers.
It is necessary for life and is found in all living matter.
It occurs in nature in the form of calcium sulphate (gypsum) and calcium carbonate (lime stone, marble and chalk).
Calcium is an essential constituent of bones and teeth. Some of its compounds are used in industry.
It occurs as magnesite, dolomite, carnallite as well as in many compounds.
Its compounds are used in medicine.
It is used in light weight alloys, in photography and incendiary bombs.
It is essential to life also as it occurs in chlorophyll.
It is a silver white, liquid form metal, widely used in thermometers, barometers, manometers and many scientific apparatus.
Its compounds are poisonous and are used in medicines. It is a very heavy metal. Its specific gravity is 13.6.

15. Important Chemical Processes

1. Bessemer Process : It is a method of converting pig iron to steel by blowing air though the molten metals to oxidize impurities such as carbon, silicon, phosphorous and manganese normally present in pig iron.
2. Clemmensen Reduction : It is a process used to convert aldehydes and ketones to the corresponding hydrocarbons by heating with amalgamated zinc and hydrochloric acid.
3. Gatterman Reaction : It is a process used to convert an aromatic amine into the corresponding halogen derivative through diazonium salt formation using copper as a catalyst.
4. Haber Process : An industrial process of producing ammonia by the reaction of nitrogen with hydrogen in the presence of a catalyst.
5. Kolbe Reaction : It is used for the preparation of saturated or unsaturated hydrocarbons by the electrolysis of solution of the alkali salts of aliphatic carboxylic acids.
6. Solvay Process : It is a process of shaking sodium carbonate from calcium carbonate and sodium chloride in large scale.

The Process involves heating of calcium carbonate to give calcium oxide and carbon dioxide which is bubbled into a solution of sodium chloride in ammonia, Sodium hydrogen carbonate is precipitated which on heating gives sodium carbonate.
7. Bayer Process : A process used to extract aluminium oxide Al2O3 or aluminium by treating powdered bauxite with hot caustic soda solution under pressure.
The process was developed by German chemist, Karl Joseph Bayer in 1888.
8. Bergius Process : A process for making lubricants and synthetic fuel e.g., petrol, from coal by heating a mixture of powdered coal and heavy oil or tar with hydrogen under pressure in the presence of a catalyst (iron, tin or lead).
The process was developed by German chemist, Friedrich Bergius, who shared the 1931 Nobel Prize.
9. Bosch Process : A process used to make industrial hydrogen by passing steam over white-hot coke to produce water gas (a mixture of carbon monoxide and hydrogen) which in the presence of a catalyst (a metal oxide) reacts with more steam to liberate hydrogen and carbon dioxide.
The process is named after the German Chemist. Carl Bosch (1874 – 1940).
10. Down Process : It is a process of making sodium metal by electrolysis of molten sodium chloride.
The molten sodium and calcium formed at the cathode are separated.
11. Frasch Process : It is used to extract sulphur from subterranean deposits in which superheated water is forced down the deposits which melts the sulphur under the ground.
Molten sulphur is collected by forcing compressed air from another side. The process was developed by German chemist, Herman Frasch 1891.
12. Hall – Heroult Process (Hall – Heroult) : A process used to a prepare aluminium by electrolysis in which alumina (aluminium oxide) is dissolved in cryolite (sodium aluminium fluoride) and electrolyzed.
It was developed in 1885 in USA by Charles Hall and in France by PT Heroult.
13. Parkes Process : A process used for extraction of silver traces from lead are galena Molten zinc is added to molten galena and lead is separated leaving zinc – silver which on heating distills off zinc freeing the silver.

16. Important General Chemical Tests.
1. Brown – Ring Test :
It is used for chemical analysis of nitrates in which the solution to be tested is mixed with iron sulphate solution in a test tube and concentrated H2SO4 (sulphuric acid) is carefully poured along the side of the test tube.
In nitrate containing substances a brown ring is formed where the layer of acid touches the solution (FeNO)SO4.
2. Flame Test :
It is used to identify certain elements in which a clean platinum wire is dipped into the mixture to be tested and the wire is heated using a busen flame.
The presence of certain elements can be detected by the change in the colour of flame.
For example, a brilliant organe – yellow will indicate sodium; crimson, strontium; and apple green barium.
3. Beilstein’s Test :
It is used for the detection of halogen in an organic compound in which a clean copper wire is heated in an oxidizing flam till the flame is no longer green.
The wire is then dipped in a solution of the substance to be analyzed and heated again. If CI, Br or I is present the flame turns a bright green.
4. Fehling’s Test :
It is used to detect sugars and aldehydes in a solution. Equal amounts of solution of copper sulphate (Fehling A) and sodium tartrate (Fehling B) are mixed in a test tube, On boiling this with a given solution a red precipitate forms is sugar or aldehyde is present.
5. Kjedahl Method :
It is used to measure nitrogen in an organic compound. The compound boiled with concentrated sulphuric acid and copper sulphate (catalyst) to convert nitrogen to ammonium sulphate.
An alkali is added to the mixture and boiled to distill of ammonia which is passed into a standard acid solution and estimated by titrating the solution.
6. Molish’s Test :
It is used to detect carbohydrates in a solution. The solution to be tested is mixed with a small quantity of alcoholic alphanaphthol and concentrated sulphuric acid is slowly poured down the side of the test tube.

When the two liquids meet the formation of deep violet rings indicates presence of carbohydrate.
7. Rast’s Method :
It is used to determine molecular weight by measuring the depression of freezing point of a camphor by a known weight of the solute.
8. Schiffs Test :
It is used to distinguish between aldehydes and ketones. An aqueous solution of resoniline and sulphurous acid (Schiff’s reagent) is used to test for the presence of aldehydes, which oxidize the reduced from of the dye rosaniline back to its original magenta colour.
The aldehydes restore the colour immediately whereas ketones, restore the colour slowly.
17. Important Laws in Chemistry
Boyle’s Law
It states that when any gas is expanded or compressed at constant temperature, its volume (V) and pressure (P) are inversely proportional to each other.
P ∞ 1/V (or) PV = constant
Charle’s Law
It states that when any gas is expanded or compressed at constant pressure, its volume (V) is directly proportional to its absolute temperature T.
V ∞ T (or) V/T = contant (or) V1/T1 = V2/T2
Dalton’s Law of Partial Pressure
It states that the total pressure exerted by a mixture of different gases in a given space is equal of sum to partial pressure of each constituent gas where partial pressure of a gas is the pressure exerted by it, if it were to occupy the same space alone.
P = P1 + P2 + P3 +…
Law of Indestructibility
It states that matter can neither be created nor destroyed by any chemical change.
Law of Multiple Proportion
It states that when two elements combine to form more than one compound, the mass of one which combines with the fixed mass of the other bears a simple ratio to each other.
Law of Reciprocal Proportion (or Law of Equivalent Proportions)
It states that when two different elements combine with the same weight of third element the ratio in which they do so will be the same or some multiple of the ratio in which they combine with each other, e.g., The elements C and H combine with the third element O to form CO2 and H2O. Also they combine directly to form CH4 :
In CO2=> C : = 12 : 32 = 3 : 8
In H2O => H : O = 2 : 16 = 1 : 8
i.e., from this the ratio C : H = 3 : 1, Now in,
CH4 => C : H = 12 : 4 = 3 :1
Law of Constant Composition
It states that a chemical compound always consists of same elements combined together in the same proportion by mass.
Gay Lussac’s Law of Combining Volumes
It states that gases react together in volumes which bear simple and whole number ratios to one another as well as to the volumes to the gaseous products whereas the volumes being measured under same conditions of temperature and pressure.
Law of Mass Action
It states that the rate of chemical reaction is proportional to the molecular concentration of each of reacting constituents.
Faraday’s Law of Electrolysis
1.The products of electrolysis appear only at the electrodes, having weight proportional to the quantity of electricity passed.
2.The amounts of ions liberated at the various electrodes are proportional to their chemical equivalents when current passes through the different electrolytes.
Ohm’s Law
It states that the magnitude of current flowing between two ends of a conductor is proportional to the potential difference between them.
Avogadro’s Law
It states that under similar conditions of temperature and pressure equal volume of all gases contain equal number of molecules.
Raoult’s Law
It states that the vapour pressure of a solution containing non – volatile solution is directly proportional to the mole fraction of the solvent.
PA = P°A . XA, PB = P°B . XB, ΔHmix = +ive, ΔV = +ive
The solutions which obey Raoult’s law are called Ideal Solutions
1.When solvent – solvent and solute – solute interactions are stronger than solvent – solute interaction positive deviations take place.
PA > P°A . XA, PB < P°B . XB, ΔHmix = +ive, ΔV = +ive
2.When solvent – solvent and solute – solute interactions are weaker than solvent – solute interaction negative deviation takes place.
PA < P°A . XA, PB < P°B . XB, ΔHmax = -ive, ΔV = -ive

18. Nuclear Reaction and Atomic Energy
Nuclear Reaction :
A Nuclear Reaction is one in which a nucleus bombarded with an elementary particle (like neutron, proton, etc) or with another nucleus to produce other products in a very shot time span.
The first nuclear reaction was discovered by Rutherford in 1919 when he bombarded nitrogen with alpha particles.
Nuclear Fission :
Nuclear Fission is the fragmentation of a large nucleus into two smaller nuclei and the liberation of large amount of energy.
In 1939 the German scientists Otto Hahn and F steersman observed that when uranium was bombarded with slow neutrons, then two smaller products were obtained with a tremendous amount of heat.
The splitting of uranium was called nuclear fission.
Types of Nuclear Fission :
1. Controlled Nuclear Fission : Carried out in nuclear reactors in which rate of fission reaction is reduced and energy produced can be used for constructive purposes.
2. Uncontrolled Nuclear Fission : In an atom bomb uncontrolled fission takes place. A very large amount of heat is produced and the process continues until the entire amount of fissionable material is exhausted.
First Atom Bomb :
On August 6, 1945, an atom bomb was dropped on Hiroshima city in Japan.
The second bomb was dropped on Nagasaki, another city of Japan on August 9, 1945. The bomb was made of Plutonium – 239.

Nuclear Fusion :
It is nuclear reaction in which lighter nuclei fuse to form a nucleus of greater mass.
In this reaction also an enormous amount of heat is produced.
By carrying on nuclear fusion under controlled conditions, the large amount of energy could be made available for useful purpose.
Atomic Energy (Nuclear Energy)
Energy produced by nuclear fission or nuclear fusion is called nuclear energy or atomic energy.
In nuclear reactions there is loss of mass. This mass is converted into energy.
It can be transformed into electrical and mechanical energy which can be used for various peaceful purposes.
19. List of Ores of Metals

Names of the Elements
Chemical Formulae
Aluminium (Al)
(a) Bauxite
Al2O3 . 2H2O
(b) Corundum
(c) Kryolite
Iron (Fe)
(a) Haematite
(b) Magnetite
(c) Iron Pyrite
(d) Siderite
Copper (Cu)
(a) Copper Pyrite
(b) Copper Glance
(c) Malachite
2CuCO3 . Cu(OH)2
Names of the Elements
Chemical Formulae

Zinc (Zn)
(a) Zinc Blende

(b) Calamine

Sodium (Na)
(a) Rock Salt

(b) Sodium Carbonate

Potassium (K)
(a) Karnalite
KCI MgCl . 6H2O

(b) Salt Petre

Lead (Pb)
(a) Galena

(b) Anglesite

Tin (Sn)
(a) Tin Pyrites
Cu2 FeSnS4

(b) Cassiterite

Silver (Ag)
(a) Silver Glance

Gold (Au)
(a) Calverite

(b) Syvanite

Mercury (Hg)
(a) Cinnabar

(b) Calomel

Magnesium (Mg)
(a) Dolomite
MgCO3 . CaCO3

(b) Karnalite
KCl MgCl2 . 6H2O

Calcium (Ca)
(a) Lime Stone

(b) Dolomite
MgCO3 . CaCO3

Phosphorous (P)
(a) Phosphorite

(b) Floreapetite

20. Oxidation and Reduction in Chemistry

  • Removal of hydrogen atom is oxidation while addition of hydrogen atom is reduction.
  • Addition of oxygen atom is oxidation while removal of oxygen atom is reduction.
  • Increase in valency of an element is oxidation while decrease in valency of an element is reduction.
  • Addition of an electronegative element is oxidation and removal is reduction.
  • Removal or electropositive element is oxidation and addition is reduction.
  • Loss of electrons is oxidation and gain of electrons is reduction.
  • Increase in oxidation number is oxidation while decrease in oxidation number is reduction.
Rules for Finding Oxidation Numbers :
  • Oxidation number of element in free state is zero i.e., P4 (oxidation number) 0
  • Alkali metals (Na, K, Li, Cs etc.) and Alkaline earth metals (Ca, Mg, Ba, Sr etc.) have +1 and +2 oxidation number respectively.
  • Oxidation number of hydrogen is +1 except in metal hydride in which its oxidation number is -1. i.e., LiH (oxidation number of hydrogen atom) = 1
  • Oxidation number of oxygen atom is always equal to -2 except.
  • F2O (in this compound the oxidation number of oxygen is +2).
  • The oxidation number of oxygen atom in all peroxides is equal to -1.
Oxidizing and Reducing Agents
Compounds having higher oxidation number will be more acidic and act as oxidizing agent and compounds having lower oxidation number will be less acidic and act as reducing agent.
Generally, compounds with oxygen atom are called oxidizing agent and compounds with hydrogen atom are called reducing agent.
  • H2O2 acts as an oxidizing agent when it is reduced to H2O.
  • H2O2 acts as a reducing agent when it is oxidized to O2 or O3.
  • H2S acts as a reducing agent when it is oxidized to sulphur.
  • Halogens act as oxidizing agent and they are reduced to halogen acids.

21. Periodic Table of Elements in Chemistry.
Mandeleev’s Periodic Law (1869)

“The physical and chemical properties of elements are a periodic function of then atomic weights, i.e., when the elements are arranged in order of their increasing atomic weights, elements with similar properties are repeated after certain regular intervals”.
Modern Periodic Law
“The physical and chemical properties of the elements are a periodic function of then atomic numbers, i.e., when the elements are arranged in order in order of their increasing atomic weights, elements with similar properties are repeated after certain regular intervals”.
Cause of Periodicity
The cause of periodicity in properties is the repetition of similar outer electronic configurations at certain regular intervals.
Main features of Modern Periodic Table
  • It has 7 horizontal rows called periods and 16 vertical columns called groups or families.
  • The first period is the shortest period consisting of 2 elements.
  • The second and third periods contain 8 elements, a fourth and fifth period contains 18 elements, sixth period contains 32 elements and seventh period is incomplete with 27 known elements.
  • The elements of second period are known as bridge elements.
  • The elements of I, II, XIII, XIV, XV, XVI, XVII and XVIII groups are collective known as normal or representative elements.
  • The elements of XVIII group are known as inert gases or noble gases.
  • The elements of III group to XIII group are known as transition elements. This is because their properties lie between the properties of the reactive metals (alkali and alkaline earth metals) placed on extreme left and the non – metals (halogens and chalcogens = oxygen family) placed on extreme right of the periodic table. Their general electronic configuration is (n – 1)d1-10ns0-2.
  • The series of elements with Z = 58 to Z = 71 which occur in periodic table after lanthanum are called lanthanides or lanthanoids. The series of elements with Z = 90 to Z = 103 which occur in the periodic table after actinum are called actinides or actinoids. These elements (lanthanides and actinides) are also known as inner transition elements. The electronic configuration is,
(n – 2) f0-14 (n – 1) d0 – 1ns²
s – Block Elements

Elements in which the last electron enters the s – orbital.
General configuration is: ns1 – 2.The elements of I and II groups are s – block elements.

Properties :
  • They are soft metals with low melting and boiling points.
  • They have low ionization energies and high electro positivity.
  • Their metallic character and reactivity increase in a group.
  • They lose the valence electrons readily to form +1 and +2 ions.
  • They are strong reducing agents.
  • They are good conductors of heat and electricity.
p – Block Elements
Elements in which the last electron enters any one of the three p – orbitals.
General configuration is : ns²np1 – 6. The XIII to XVIII groups (excluding He) have p – block elements.
The elements of XVII group are known as halogens (salt producers) and that of XVI group are known as chalcogens (ore – forming).
Properties :
  • The metallic character increases within a group and decreases along a period.
  • Their ionization energies are relatively higher than that of s – block elements.
  • They show more than one oxidation states.
  • Their oxidizing character increase in a period and reducing character increases along a group.
d – Block Elements
Elements in which the last electron enters any one of the five d – orbitals.
General configuration is (n – 1)d1 – 10 ns0 – 2. The elements of groups III to XII belong to this category.
They are called transition elements.
  • They are hard, malleable and ductile metals with high m.p. and b.p.
  • They are good conductors of heat and electricity.
  • Their ionization energies are between s and p – block elements.
  • Their compounds are generally coloured and paramagnetic.
  • They show variable oxidation states.
  • They form both ionic and covalent compounds.
  • Most of the transition elements form alloys.
f – Block Elements
Elements in which the last electron enters any one of the seven f – orbitals.
General configuration is (n – 2)f0 – 14 (n – 1)d0 – 1ns². There are 28 f – block elements in all (Lanthanides and Actinides).
They are called inner – transition elements.
Properties :
  • They are heavy metals with high m.p. and b.p.
  • They show variable oxidation states.
  • Their compounds are generally coloured.
  • They have a high tendency to form complexes.
  • Most of the elements of the actinide series are radioactive.
Prediction of Period, Group and Block
  • For s – block elements group number is equal to the number of valence electrons.
  • For p – block elements group number is equal to 10 + number of valence electrons.
  • For d – block elements group number is equal to the number of electrons in (n – 1)d – subshell + number of electrons in valence shell.
22. Principles in Chemistry
Pauli’s Exclusion Principle

It states that “No two electrons in an atom can have the same set of four quantum numbers”.
In other words “An orbital can have a maximum two electrons and these must have opposite signs”.
Aufbau Principle
It states that “Orbital of lowest energy is filled first, before the filling of orbitals having higher energy starts”.
So, the order of relative energies is : 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d and so on.
(n + l) Rule
Lower the value of (n + l) for an orbital, the lower is its energy.
If two orbitals have same (n + l) value, the orbital with lower value of n has lower energy and hence is filled first.
Exceptions of Aufbau Principle
The electronic configurations having half – filled or completely filled orbitals are more stable.
In light of this fact the electronic configurations of Cu (29) and Cr (24) can be studied as follows :
The electronic configuration of Cr24 according to Aufbau’s principle :
1s², 2s², 2p6, 3s², 3p6, 4s², 3d4
The actual configuration of Cr24 : 1s², 2s², 2p6, 3s², 3p6, 4s¹, 3d5
Since 3d subshell is more stable when it has 5 electrons in it i.e., it is half filled so the latter configuration is actual and more stable of Cr.
The elements not obeying Aufbau’s principle
Cr24, Cu29 Nb41, Mo42, Tc43, Ru44, Rh45, Pb46, Ag47, La57, Gd64, Pt78, Au79 etc.
Hund’s Rule of Maximum Multiplicity
It states that “Electron pairing in any orbital (s, p, d, f) cannot take place until each orbital of the same sublevel contains one electron.”
e.g., O8=>2, 6
1s², 2s², 2p4
1s², 2s², 2p²x, 2p¹y, 2p¹z
Heisenberg’s Uncertainity Principle (1926)
It states that “It is impossible to specify at any given moment both the position and momentum of an electron.”
If δx and δp be the uncertainties with respect to the position and the momentum, then uncertainty principle can be expressed as:
Δx . Δp ≥ h/4 π
Bohr’s Principle
It states thatx “An electron can resolve only in those orbits whose angular momentum (mvr) is an integral multiple of the factor (h/2π)”

Bohr – Bury Scheme
  • The maximum no. of electrons in each shell is 2n², where n is the principal quantum number.
  • The maximum no. of electrons in outermost orbit can be 8 and in its penultimate orbit can be 18.
  • The outermost shell can contain not more than 2 electrons, if the next to the outermost has not reached its maximum requirement (e.g.),
  • Ca20 2, 8, 8, 2;
  • Sc21 2, 8, 9, 2;
  • Zn30 2, 8, 18, 2;
  • Kr36 2, 8, 18, 8;
  • Rb37 2, 8, 18, 8, 1.
23. Quantum Numbers in Chemistry
The set of four numbers which give complete information about the electron in an atom i.e., energy, orbital occupied, size, shape and orientation of that orbital and the direction of electron spin.
(a) Principal Quantum Number (n)
It gives the major energy level to which the electron belongs.
Thus, n = 1, 2, 3,… etc depending upon whether the electron belongs to first, second, third etc. energy levels For the first energy level (K – shell) n = 1, for second (M – shell) n = 2, etc.
(b) Azimuthal (or) Subsidiary (or) Angular Momentum Quantum Number (I)
It gives the energy level of subshells. It gives the following information :
  • Number of subshells present within a main shell.
  • Shapes of subshells.
  • Contribution of energy due to angular momentum towards the total energy of the electron.
  • For a given value of n, l can have values from 0 to (n – 1).
  • For n = 1(K), l = 0 i.e. one subshell (s)
  • n = 2 (L), I = 0, 1 i.e., two subshells (s, p)
  • n = 3 (M), l = 0, 1, 2 i.e., three subshells (s, p, d)
  • n = 4 (N), I = 0, 1, 2, 3 i.e., four subshells (s, p, d, f)
Order of energies : s < p < d < f
It was proposed by Sommerfeld.
(c) Magnetic Quantum Number (m)
It tells the number of orditals present within the same subshell.
For a given value of I, m can have values from -l to +l including 0, making a total of (2l + 1) values.
These quantum number also give the orientation of the orbital.
The number of orbital in a shell with principal quantum number n is equal to n²
The orbitals having same energy level are called degenerate orbitals.

No. of Orbitals
-1, 0, +1
-2, -1, 0, +1, +2
-3, -2, -1, 0, +1
+2, +3

It was given by Lande to explain Zeeman and Stark effects.
(d) Spin Quantum Number (s)
This arises due to the spinning of the electron about its own axis.
It can be clockwise represented by +1 / 2 or or anticlockwise represented by -1/2.
This is the only quantum number that has non – integral values. It was introduced by Uhlenbeck and Goudsmet.
Distribution of Electrons in Quantum Levels :
S. No
No. of Electrons
Total Electrons
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
+1/2, -1/2
24. Radioactivity in Chemistry
A phenomenon of spontaneous disintegration, first observed in certain naturally occurring heavy elements like radium, actinium, uranium, thorium, etc, with the emission of alpha, beta and gamma rays.
It is the property of the nuclide to disintegrate in which a transformation takes place of a relatively unstable nuclide to relatively stable nuclide accompanied with the emission of particles or electromagnetic radiation.
The nuclide that decays is said to be radioactive.
Discovery of Radioactivity
The phenomenon was accidentally discovered in 1896 by French physicist Henry de Becquerel.
He observed that uranium mineral gave off invisible radiation. He termed this property of uranium radioactivity. Later Pierre and Madam Curie showed similar phenomenon in other metals like poeonium, francium and radium.
Radioactive Emissions
(i) Sub – Atomic Particles (Radiation)
  • Alpha (α) Particles : A positively charged helium atom which has very little penetrating power. They can be absorbed by a sheet of paper or stopped by aluminium foil.
  • Beta (β) Particles : A negatively charged light particle. Its penetrating power is greater than that of alpha – ray.
(ii) Penetrating Particles (Radiation)
Also called Gamma (γ) emission. These are electromagnetic radiations of low wavelength, high frequency, and high energy. Their penetrating power is very great as they can pass through several centimetre of lead.
Important Terms of Chemistry
(a) Metals : Metals comprise 75% of all known elements and appear on the left hand side of the periodic table.
Metals are solids at room temperature (except mercury, gallium and francium).
They are malleable, ductile and good conductors of heat and electricity.
(b) Non – Metals : These can be gases, liquids or even solids with low m.p and b.p. Most of them are brittle and are neither malleable nor ductile.
(c) Metalloids : The elements which show the properties of both metals and non – metals are known as metalloids or semi – metals.
(d) Valency :
  • The valency of a metal is equal to number of valence electrons. The electrons present in outer- most orbit are called valence electrons. (or)
  • Valency is equal to the number of hydrogen atoms or twice the number of oxygen atoms which combines with one atom of an elements. (or)
  • The valency of a non – metal elements is usually equal to eight minus the number of valence electrons in its atom.
  • The atoms combine with each other since; they have a tendency to acquire eight electrons (except hydrogen atom) in its outermost orbit. The atoms which give outermost electrons acquires positive charge and other which take electrons acquire negative charge.
(e) Atomic Radius : The distance between the centre of nucleus and the outer most shell of electrons.
(f) Van der Waal’s Radius : Half of the distance between the nuclei of two adjacent atoms belonging to two neighbouring molecules of an element.
(g) Ionic Radius : The distance from the nucleus of an ion up to which it has influence on its electron cloud.
(h) Ionization energy (Ionization potential or Ionization enthalpy) : The minimum amount of energy required to remove an electron from an atom.
The ionization energies required to remove first second and third etc., electrons from an atom are called successive ionization energies.
Remember that Third IE > Second IE > First IE
Ionization energy is governed by the factors :
  • Nuclear Charge : Energy increases with increase in nuclear charge
  • Atomic Size : Energy decreases with increase in size
  • Penetration effect of the Electrons : Energy increases with increase in penetration effect
  • Screening effect of the Inner Shell Electrons : Energy decreases with increase of screening or shielding effect
  • Effect of half – filled or completely filled Orbitals : If an atom contains half – filled or completely filled orbitals then it is more stable, so the energy required is more than expected.
25. Water
Of the total global water, the oceans and inland saline water bodies hold 97.3% and the fresh water amounts to only 2.7%.
Water constitutes about 65% of our body and is an essential element for its growth.
  • The density of ice is less than that of water and hence ice floats over water.
  • Water has maximum density (1 g) at 4°C.
  • M.P. is 273.2 K and B.P. is 373.2 K
Heavy Water
  • Chemically heavy water is deuterium oxide (D2O).
  • It was discovered by Urey in 1932.
  • It is colourless, odourless and tasteless liquid.
  • It has been finding use in nuclear reactors as a moderator because it slows the fast moving neutrons.
  • Its MP is 276.8 K and BP is 374.4 K.

Properties of water: The freezing point, boiling point, heat of fusion and heat of vaporisation of water are higher as compared to the hydrides of the other members of same group of oxygen.
Hard and Soft Water: Water which produces lather with soap solution readily is called soft water, e.g., Rain – water, dematerialized water. Water which does not produce lather with soap solution readily is called hard water. e.g.. Sea – water, river water, well water, tap – water.
Cause of Hardness of Water
The hardness of water is due to presence of the bicarbonates, chlorides and sulphates of calcium and magnesium (Ca++ and Mg++).
Types of Hardness of Water
(A) Temporary Hardness
This type of hardness in water is due to the presence of bicarbonates of calcium and magnesium. It can be removed by boiling.
(B) Permanent Hardness
This type of hardness is due to presence of bicarbonates of calcium and magnesium, it can be removed by boiling but some chlorides and sulphates of calcium and magnesium are also present with it which can not be removed by boiling.
Softening of Water
The process of removal of hardness from water is called softening of water.
  • Water is treated with a calculated amount of washing soda (Na2CO3) which converts the chlorides and sulphates of calcium and magnesium into their respective carbonates.
  • Iron Exchange Method : This method can be classified into two parts :
(A) Inorganic cation Exchanges : This method is also known as “Permutit Method”.
These are complex inorganic salts like “hydrated sodium – aluminium silicate” (Na2Al2Si2O8 . xH2O) which have interesting property of exchanging cations such as calcium and magnesium ions in hard water with sodium salt ions.
These complex salts are known as “Zeolites”.
(B) Organic ion Exchanges : These are complex organic molecules having giant hydrogen frame work attached to acidic or basic groups.
These are called ion exchange resins.
These are superior to zeolites because they can remove all types of cations as well as anions present in water. The resulting water is known as deionised water or dematerialized water.
Note : Mass of 1 mole of D2O and T2O are 20 gm and 22 gm respectively.