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PERIODIC PROPERTIES

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  ATOMIC RADIUS Atomic radius is defined as the distance from the center of the nucleus to the outer most shell of electrons.  Probability of finding the electron is never zero even at large distance from the nucleus. Based on probability concept, an atom doesn't have well defined boundary. Hence it is very difficult to determine the atomic radius.  Atomic radius is taken as the effective size which is the distance of the closest approach of one atom to another atom in a bonding state.  The atomic radius can be determined as (a) Covalent radius (b) Vander waal's radius (c) Metallic radius (d) Ionic radius Covalent radius One half of the inter-nuclear distance between the two covalently bonded atom is called covalent radius.  Covalent radius can be determined in case of the atoms which are attached to each other by covalent bond.  r covalent = Inter-nuclear distance between two covalently bonded atoms / 2 (i) For homoatomic molecules d A-A = r A + r A Or,...

BLOCKS OF ELEMENTS

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  Periodic table is divide into 4  blocks known as S, p, d, f  blocks. The classification of the elements depends upon the type of sub-shell in which last electron of the element enters.  S - Block elements   The element in which last electron enters into s - subshell  are called s - block element.  The general electronic configuration of s - block elements are  ns 1-2   .  The s - block elements are present in the left side of the periodic table.  Group 1 and Group 2 elements as well as Helium of zero group are known as the s - block elements. All s - block elements are normal elements. Characteristics of s - block elements (i) The elements have low ionization energy.  (ii) They are soft metal having low melting and boiling point.  (iii) They are highly reactive.  (iv) They are good reducing agents.  (v) They give to the flame.  p - block elements The elements in which last electrons enters into p - subshel...

DESCRIPTION OF GROUPS IN THE LONG FORM OF PERIODIC TABLE

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The vertical columns starting from top to bottom are called groups.  There are 18 groups in the periodic table and the groups are denoted by IA to VIIA, IB to VIIB, VIII (three columns), Zero group.  According to latest convention the groups are number as 1 to 18. CHARACTERISTICS OF GROUPS (1) Valency  :- Valency of all the elements in a group are same.  Ex:- All the elements of group 1 , i.e. Li, Na, k, Rb, Cs, Fr have the valency one.  (2) Similar properties :- All the elements of same group have similar properties as they have same valencies.  Ex:-All elements of group 1 have low ionization energy.  (3) Prediction of properties  :- The group number of an element helps to predict the property of that element, by knowing the property of one element and the properties of other elements in the same group can be predicted.  (4) Gradation of properties  :- The elements of same group have gradually change in properties with increasing in ato...

LONG FORM OF PERIODIC TABLE

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In Long form periodic table elements have been arranged in the increasing order of their atomic mass and also based on electronic configuration.  This periodic table consists of (i) 7 horizontal rows known as periods.  (ii) 18 vertical columns known as groups.  (iii) 4 blocks Periods There are seven periods in the periodic table. The number of elements in each period corresponds to number of electrons in different major energy levels. Each period starts with a new principle quantum number.  The horizontal rows from left to right in the periodic table are called periods.  There are 7 horizontal rows. So there are 7 periods.  The number of elements in each period corresponds to number of electron in different energy levels.  1 st  PERIOD This period corresponds to first energy level, whose capacity is two electrons. So there are two elements present in the 1st period. They are H(1s 1 ) , He (1s 2 ) . It is the shortest period.  2nd  PERIOD...

MODERN PERIODIC TABLE

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It was discovered by Moseley.   It was based on atomic number.  Modern periodic law :-   The physical and chemical properties of elements are periodic function of their atomic number . That is if the elements are arranged in the increasing order of their atomic number . Then the similar properties of element are repeated after a regular intervals, i.e. 2,8,8,18,18,32. Characteristics of modern periodic table  :- Elements are classified according to their atomic number.  Ther periods e are 9 vertical groups and 7 horizontal periods The groups upto VII - 7 groups , VIII - 1group, '0' - 1 group '0' - group elements are called Inert gas or Noble gas group. This group was discovered by Ramsay. 

PERIODIC CLASSIFICATION

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  PERIODIC TABLE  :- The method of arranging similar elements in one group and separating them from dissimilar elements is called classification of elements.  A table which has been formed by the classification of elements is known as periodic table.  Mendeleev's Periodic Table  :- Mendeleev arranged sixty three elements in a table on the basis of periodic law, which states that physical and chemical properties of the elements are the periodic function of their atomic masses i.e. when elements are arranged in the increasing order of atomic masses similar elements are repeated after regular intervals.  Advantages of Mendeleev's periodic table   (1) Prediction of new element  :- In Mendeleev's periodic table there were many vacant spaces. He had predict the properties of elements that would occupy when discovered. When few elements were later discovered they were found to be similar properties as predicted by Mendeleev.  Ex :-   Eleme...

RADICAL or ION

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  A radical may be defined as an atom or group of atoms having positive or negative charge and behaves as a single unit in chemical changes.  In the other words, all ionic compounds are made up of two opposite charged parts is called a radical.  Radical are of two types depending upon the nature of charge carried by them.  (i) Electro positive radical or Basic radical or Cation (ii) Electric negative radical or Acid radical or Anion Electro positive radical or Basic radical or Cation  :- The radical having a positive charge on it is known as Basic radical.  Ex :- Na+, K+, Ca2+ etc.  Electro negative radical or Acid radical or Anion  :- The radical having a negative charge on it is known as Acid radical.  Ex :- Cl-, F-, I- etc.  Radicals can be classified as follows :- (a) Simple radicals (b) Compound radicals Simple radicals  :- It is a radical containing only one kind of atom  Ex:- Na+, K+, Ca2+, Cl-, F-, I- etc.  Compoun...

VALENCY OF ELEMENTS

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  VALENCY Definition :- It is defined as the number of electrons lost, gained or shared by one atom of an element in order to attain the stable configuration of inert gas element.  Ex :- In sodium chloride, sodium losses one electron to attain the stable configuration. Chlorine gains one electron and attains the stable configuration.  Therefore in NaCl, the valency of Na is +1 and Cl is -1 .  Sodium            Chlorine Symbol -                Na                                Cl Atomic number-    11                                17 Electronic Configuration -     2,8,1                         2,8,7   Na+ (2, 8)        ...

FORMULA OF A SUBSTANCE

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  FORMULA  :- Formula is the symbolic representation of the molecule of a substance.  Ex :- Water is represented by H 2 O, Sodium chloride is represented by NaCl etc.  Formula can be classified into three types:- i) Empirical / Simple formula ii) Molecular formula iii) Structural formula Empirical formula   In this type of formula, the ratio between the atoms of the various elements present in one molecule of the compound.  OR The simplest formula of the compound is called empirical formula.  Ex :- Actual formula of glucose is C 6 H 12 O 6   but its empirical formula is CH 2 O (1:2:1).  Molecular formula   It is defined as the actual number of atoms of the various elements present in one molecule of the compound. Ex :- Molecular formula of glucose is C 6 H 12 O 6   . It is made up of 6 atoms of'C' , 12 atoms of 'H' and 6 atoms of 'O'. Structural formula   In this type of formula, the atoms of various elements are link...

SYMBOLS OF ELEMENTS

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  SYMBOL  :- It is defined as an abbreviation (short hand sign) for the full name of an element.  Ex :- Hydrogen is represented by the symbol 'H' Oxygen is represented by the symbol 'O'  The first letter of the symbol is always capital while the second one is always small.  Ex :- Symbol of Nickel is 'Ni' not 'NI'.  List of some Elements   1- Hydrogen                     H 2- Helium                          He 3- Lithium                         Li 4- Beryllium                     Be 5- Boron                             B 6- Carbon                           C 7- Nitrogen ...

ATOM

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  ATOM :- An atom is defined as the smallest particles of an element which may or may not have independent existence.  Ex :-(i) Atoms of Cu, Fe etc.have independent existence.  (ii) Atoms of hydrogen, Oxygen etc.don't have independent existence.  MOLECULE  :- A molecule is defined as the smallest particle of an element or a compound which has independent existence.  Ex  :- CO 2 , O 2 , N 2 , etc.  Molecules can be classified into two types (I) Homoatomic molecules (II) Heteroatomic molecules Homoatomic molecules  :-In this type, two or more atoms of the same element combine to form molecules.  Ex :- i) Mono atomic molecules  :- They contain single atoms of the same element. He, Ne etc.are mono atomic molecules.  ii) Di atomic molecules   :- They contain two atoms of the same element. Oxygen (O 2 ) , Nitrogen (N 2 )  etc.are diatomic molecules.  iii) Tri atomic molecules  :- They contain three atoms of t...

MATTER

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MATTER  :- Matter is defined as anything that has weight and occupies space.  Ex  :- air, salt, water etc.  It can be classified into two categories:- (A) Physical classification (B) Chemical classification Physical classification   (I) SOLID STATE  :- Solids have definite shape and volume.  Ex :- Copper, Silver etc.  (II) LIQUID STATE  :- Liquids have definite but no shape.  Ex :- Water, Milk, oil etc.  (III) GASEOUS STATE  :- Gases have neither volume nor shape.  Ex :- Hydrogen, Oxygen etc.  Chemical classification   (i) HOMOGENEOUS MATTER  :- Matter that has uniform composition and identical properties throughout the phase is called homogeneous matter.  Ex:-  Water, sugar, oxygen etc. (A solution is also called homogeneous mixture)  (ii) HETEROGENEOUS MATTER  :-This type of matter is made of two or more components which are physically distinct.  Ex :- Mixture of sand and sulphur, ...

ISOMERISM

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  Two or more compounds having same molecular formula but different physical and chemical properties are called Isomers and the phenomenon is called Isomerism.  It is mainly classified into two types.  1- Structural Isomerism 2- Stereo Isomerism Structural Isomerism :-  The structural Isomers are those Isomers in which the atoms are completely arranged in different order with the same molecular formula.  There are six types of structural Isomerism i.e (a) Chain Isomerism (b) Position Isomerism (c) Ring chain Isomerism (d) Functional Isomerism (e) Metamerism  (f) Tautomerism Chain Isomerism     When two or more compounds having same molecular formula  but different arrangement of the carbon chain then such compounds are called chain Isomers and the phenomenon is called chain Isomerism.      Ex-    Position Isomerism   The compounds having same molecular formula but different position of the functional group, carbo...