IAS IPS Coaching Centre in Coimbatore

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Har Gobind Khorana

Har Gobind Khorana, was born in 1922. He obtained his M.Sc. degree from Punjab University in Lahore. He worked with Professor Vladimir Prelog, who moulded Khorana’s thought and philosophy towards science, work and effort. After a brief stay in India in 1949, Khorana went back to England and worked with Professor G.W. Kenner and Professor A.R.Todd. It was at Cambridge, U.K. that he got interested in both proteins and nucleic acids. Dr Khorana shared the Nobel Prize for Medicine and Physiology in 1968 with Marshall Nirenberg and Robert Holley for cracking the genetic code.

Victor Grignard

Victor Grignard had a strange start in academic life for a chemist - he took a maths degree. When he eventually switched to chemistry, it was not to the mathematical province of physical chemistry but to organic chemistry. While attempting to find an efficient catalyst for the process of methylation, he noted that Zn in diethyl ether had been used for this purpose and wondered whether the Mg/ether combination might be successful. Grignard reagents were first reported in 1900 and Grignard used this work for his doctoral thesis in 1901. In 1910, Grignard obtained a professorship at the University of Nancy and in 1912, he was awarded the Nobel prize for Chemistry which he shared with Paul Sabatier who had made advances in nickel catalysed hydrogenation.

Alfred Werner (1866-1919)

Werner was born on December 12, 1866, in Mülhouse, a small community in the French province of Alsace. His study of chemistry began in Karlsruhe (Germany) and continued in Zurich (Switzerland), where in his doctoral thesis in 1890, he explained the difference in properties of certain nitrogen containing organic substances on the basis of isomerism. He extended vant Hoff’s theory of tetrahedral carbon atom and modified it for nitrogen. Werner showed optical and electrical differences between complex compounds based on physical measurements. In fact, Werner was the first to discover optical activity in certain coordination compounds.
He, at the age of 29 years became a full professor at Technische Hochschule in Zurich in 1895. Alfred Werner was a chemist and educationist. His accomplishments included the development of the theory of coordination compounds. This theory, in which Werner proposed revolutionary ideas about how atoms and molecules are linked together, was formulated in a span of only three years, from 1890 to 1893. The remainder of his career was spent gathering the experimental support required to validate his new ideas. Werner became the first Swiss chemist to win the Nobel Prize in 1913 for his work on the linkage of atoms and the coordination theory.

Principal Ores of Some Important Metals

Aluminium - Bauxite,  Kaolinite (a form of clay)

Iron  -   Haematite,  Magnetite,  Siderite,  Iron pyrites

Copper - Copper pyrites,  Malachite,  Cuprite,  Copper glanc

Zinc - Zinc blende or Sphalerite ZnS, Calamine,  Zincite ZnO

The Solid State

Solids have definite mass, volume and shape. This is due to the fixed position of their constituent particles, short distances and strong interactions between them. In amorphous solids, the arrangement of constituent particles has only short range order and consequently they behave like super cooled liquids, do not have sharp melting points and are isotropic in nature. In crystalline solids there is long range order in the arrangement of their constituent particles. They have sharp melting points, are anisotropic in nature and their particles have characteristic shapes. Properties of crystalline solids depend upon the nature of interactions between their constituent particles. On this basis, they can be divided into four categories, namely: molecular, ionic, metallic and covalent solids. They differ widely in their properties.
The constituent particles in crystalline solids are arranged in a regular pattern which extends throughout the crystal. This arrangement is often depicted in the form of a three dimensional array of points which is called crystal lattice. Each lattice point gives the location of one particle in space. In all, fourteen different types of lattices are possible which are called Bravais lattices. Each lattice can be generated by repeating its small characteristic portion called unit cell. A unit cell is characterised by its edge lengths and three angles between these edges. Unit cells can be either primitive which have particles only at their corner positions or centred. The centred unit cells have additional particles at their body centre (bodycentred), at the centre of each face (face-centred) or at the centre of two opposite faces (end-centred). There are seven types of primitive unit cells. Taking centred unit cells also into account, there are fourteen types of unit cells in all, which result in fourteen Bravais lattices.
Close-packing of particles result in two highly efficient lattices, hexagonal close-packed (hcp) and cubic close-packed (ccp). The latter is also called facecentred cubic (fcc) lattice. In both of these packings 74% space is filled. The remaining space is present in the form of two types of voids-octahedral voids and tetrahedral voids. Other types of packing are not close-packings and have less efficient packing of particles. While in body-centred cubic lattice (bcc) 68% space is filled, in simple cubic lattice only 52.4 % space is filled.

Solids are not perfect in structure. There are different types of imperfections or defects in them. Point defects and line defects are common types of defects. Point defects are of three types - stoichiometric defects, impurity defects and non-stoichiometric defects. Vacancy defects and interstitial defects are the two basic types of stoichiometric point defects. In ionic solids, these defects are present as Frenkel and Schottky defects. Impurity defects are caused by the presence of an impurity in the crystal. In ionic solids, when the ionic impurity has a different valence than the main compound, some vacancies are created. Nonstoichiometric defects are of metal excess type and metal deficient type. Sometimes
calculated amounts of impurities are introduced by doping in semiconductors that change their electrical properties. Such materials are widely used in electronics industry. Solids show many types of magnetic properties like paramagnetism, diamagnetism, ferromagnetism, antiferromagnetism and ferrimagnetism. These properties are used in audio, video and other recording devices. All these properties can be correlated with their electronic configurations or structures.

Elements, their Atomic Number

Element/Symbol/Atomic Number      

Actinium  Ac   89

Aluminium  Al   13

Americium  Am   95

Antimony   Sb   51  

Argon    Ar   18  

Arsenic    As   33

Astatine    At   85

Barium    Ba   56  

Berkelium    Bk   97

Beryllium    Be    4

Bismuth Bi 83

Bohrium Bh 107

Boron B 5

Bromine Br 35

Cadmium Cd 48  

Caesium Cs 55

Calcium Ca 20

Californium Cf 98  

Carbon C 6

Cerium Ce 58

Chlorine Cl 17

Chromium Cr 24

Cobalt Co 27

Copper Cu 29

Curium Cm 96

Dubnium Db 105

Dysprosium Dy 66

Einsteinium Es 99

Erbium Er 68

Europium Eu 63

Fermium Fm 100

Fluorine F 9

Francium Fr 87

Gadolinium Gd 64

Gallium Ga 31

Germanium Ge 32

Gold    Au 79

Hafnium Hf 72

Hassium Hs 108

Helium He 2

Holmium Ho 67

Hydrogen H 1

Indium In 49

Iodine I 53

Iridium Ir 77

Iron        Fe 26

Krypton Kr 36

Lanthanum La 57  

Lawrencium Lr 103

Lead     Pb 82

Lithium Li 3

Lutetium Lu 71

Magnesium Mg 12  

Manganese Mn 25

Meitneium Mt 109

Mendelevium Md 101

Mercury Hg 80    

Molybdenum Mo 42  

Neodymium Nd 60  

Neon Ne 10  

Neptunium Np 93    

Nickel Ni 28    

Niobium Nb 41    

Nitrogen N 7  

Nobelium No 102  

Osmium Os 76  

Oxygen O 8  

Palladium Pd 46  

Phosphorus P 15    

Platinum Pt 78  

Plutonium Pu 94    

Polonium Po 84  

Potassium K 19  

Praseodymium Pr 59  

Promethium Pm 61  

Protactinium Pa 91  

Radium Ra 88  

Radon Rn 86  

Rhenium Re 75  

Rhodium Rh 45  

Rubidium Rb 37  

Ruthenium Ru 44  

Rutherfordium Rf 104  

Samarium Sm 62  

Scandium Sc 21  

Seaborgium Sg 106  

Selenium Se 34  

Silicon Si 14  

Silver Ag 47    

Sodium Na 11  

Strontium Sr 38  

Sulphur S 16  

Tantalum Ta 73    

Technetium Tc 43  

Tellurium Te 52  

Terbium Tb 65  

Thallium Tl 81  

Thorium Th 90  

Thulium Tm 69  

Tin     Sn 50  

Titanium Ti 22  

Tungsten W 74    

Ununbium Uub 112  

Ununnilium Uun 110    

Unununium Uuu  111  

Uranium U 92    

Vanadium V 23  

Xenon Xe 54    

Ytterbium Yb 70  

Yttrium Y 39  

Zinc     Zn 30  

Zirconium Zr 40