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 Using electronic    configuration as the criterion ,we ordinarily recognise four general type of elements ; The inert gas elements  THe representative elements  The transition elements  The inner transition elements. "The classification of these elements into these groups is dependent on the extent to which the s,p,d and f orbitals are filled". (1) Inert Gases (a) s and p _orbital of the most shell of these elements are completely filled. The outermost electronic configuration in ns2np6. (b) HElium is also inert but it's electronic configuration is 1s2. (2) Representative or normal elements:- (a) Outermost shell of these elements is incomplete. The number of electrons is the outermost shell is less than eight. (b) Inner shells are complete. (c) s-  and p-block  elements except inert gases are called normal or representative elements. (3) Transition Elements ; (a) Last two shells of these elements namely outermost and penultimate shells are incomp...

  INTRODUCTION AND DEFINATION "The distance between the centre of of the nucleus of an  ion and the point upto which the nucleus has influence on its electron cloud." The limit of electron cloud  around nucleus cannot be determined with certainty. The radius of an ion is determined by determining  the internuclear distance in an ionic compound by X-ray measurements. This distance is then taken as the sum of the radii of the two ions involved. "If we know the radius of one ion, we  can calculate the radius of the other". "The atoms change into the ions either by the loss or gain of electrons". "A cation is always smaller than the corresponding atom ,whereas anion is always bigger than the corresponding atom". VARIATION OF IONIC RADII IN A GROUP:- Since the atomic size increases as we move down the group , therefore, ionic radius also  increases in moving from top to bottom in a group. Example:- ionic radii of alkali metals may be represented as: A...

  In the long form of the periodic table, several properties of elements such as atomic radii,ionic radii,ionization potential,electronegativity etc. vary in regular way in a group and in a period. Such properties are called periodic properties. These properties depend on electronic configuration of elements. ATOMIC RADIUS:- The distance between the centre of the nucleus and the electron cloud of the outermost shell is called atomic radius. Types of atomic radius:- Covalent radius, Vander Waals radius or collision radius. Crystal radius (metallic or atomic radius). Covalent Radius  It is one half of the distance between nuclei of two like atoms joined by a single covalent bond. example:- The distance between the nuclei of two chlorine atoms in a chlorine molecule is 1.98A⁰. In a heteronuclear  Diatomic molecule AB, if both the atoms are linked by a single covalent bond and have nearly the same electronegativity , the bond length dA-B is equal to sum of covalent radii of t...

 PERIOD Each period starts with an alkali metal whose outermost electronic configuration is ns¹. Each period ends with a noble  gas  of outermost electronic configuration ns²np⁶ except He.  The number of elements in a period is equal to the number of necessary e's to acquire ns²np⁶ configuration in the outermost shell of first element (alkali metal) of the period. First period contains two elements. ELECTRONIC BASIS OF PERIODIC CLASSIFICATION:- With a better understanding of the part that the electron plays great role in the properties of the elements . According to electronic configuration, the elements may be divided into four groups:- s- block elements, p-block elements,  d-block elements. f-block elements. S-BLOCK ELEMENTS:- The elements of the periodic table in which the last electron gets filled in the s-orbital, called s-block elements. S-orbital can accomodate a maximum of two electrons. Their general formulae are ns¹ and ns² respectively. Where n = 1 to...

  INTRODUCTION:- To describe periodic properties many scientists give different type of hypothesis .Like:- Prout's  hypothesis Doberenier's  Triads The telluric Helix Newland's rule of octave  Lother mayers volume curves Mandeleef's Periodic Table. Modern periodic table. At present time we use Mandeleef  periodic table and modern periodic table  to understand the periodic properties:- According to the Mandeleef periodic table:- Periodic table is based on atomic weight. Horizontal lines are called PERIODS. Vertical lines are called  GROUPS. The periodic table is consists of SEVEN PERIODS and NINE GROUPS. The earlier periodic table had only 8 groups: the noble gases were added later in the zero group because these were not discovered when Mandeleef  put forward his periodic table. All these groups (except VIII and zero groups are divided into subgroups A and B. 2,8,18 and 32 are called magic numbers. Merits of Mandeleef's  periodic table:- Clas...

 Anything that has mass and occupies space is called matter. We classify matter in two types:- Physical classification, Chemical classification. 1. PHYSICAL CLASSIFICATION:- Classified  into three states; Solid Liquid Gas. 1.  SOLID:- Definite shape and volume,rigid and hard. example:- Wood,table,copper rod,comman salt etc. 2. LIQUID:- Definite volume but not definate shape. example:- water,milk,oil etc. 3.  GASEOUS STATE:- A gas neither possesses a definite volume nor a definite shape. example:- Air, oxygen,hydrogen,CO2etc. PARTICLE NATURE OF MATTER: * Matter made up of particles. * IN SOLIDS, the particles are closely packed and the empty spaces between the particles are very small. Example:- Solid can have only vibratory motion. *The regular oder arrangement of particles in solids is called lattice. *The attractive forces among the particles called INTER PARTICLE FORCES are strong in solid. *IN LIQUIDS, particles are loosely placed and empty spaces between them ar...

INTRODUCTION OF CHEMISTRY The branch of science wich deals with the study of composition, properties and structures of matter and the changes which the matter undergoes under different conditions and laws which govern these changes. It also plays an important role in our daily life. IMPORTANCE AND SCOPE OF CHEMISTRY All the matter in the universe is made up of tiny smallest particles called atoms or molecules. It is difficult today to imagine our life without chemistry. Main applications of chemistry 1. Chemistry has helped in agriculture, food, medicine, warfare, transportation, computers and in our everyday life. Chemistry for meeting our basic needs and necessities of life Provided chemical fertilizers, improved variety of insectisides, fugicides and pesticides to increase the yield of crops and fruits. To use of preservatives has helped to keep food materials for longer periods. Chemistry has also helped for better health and sanitation, the epidemics such as chlora, corona, smal...

 INTRODUCTION John Dalton(1766-1844),regarded as the atom is a hard, dence and smallest indivisible particle of matter. Cathode Rays:- if electric discharge from a high potential source is passed through a discharged tube evacuated to pressure around 0.01mm or less, ray are emitted from the cathode,these are called cathode rays. These rays travel in a straight lines at the right angle to the cathode surface. They produce mechanical motion in a small paddle wheel placed in their path indicating that they are material particles. These particles are deflected from their path by electric and magnetic fields showing that they are electrically charged. These particles are known as electrons. Ratio of e/m of electrons determined by J.J.Thomson. The magnetic field is applied at right angles to the direction the beam. Magnetic force = Beu B = strength of magnetic field. e = charge u = velocity electron starts moving in a circular path of radius r. The centrifugal force mv²/r arising from th...