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PERIODICITY IN PROPERTIES

TOPIC COVER:
[I]PERIODIC IN PHYSICAL PROPERTIES:
(1) ATOMIC DENSITY:
(2) ATOMIC VOLUME:
(3) MELTING AND BOILING POINT:
(4) VALENCY:
(5) SCREENING OR SHIELDING EFFECT:
(6) ATOMIC RADIUS:
(7) IONISATION POTENTIAL(IP)/ ENTHALPY:
(8) ECTRONEGATIVITY:
[II] PERIODICITY IN CHEMICAL PROPERTIES:
[III] PERIODICITY IN CHEMICAL REACTIVITY:
[IV] SOME FACTS ABOUT ELEMENTS:
 
PERIODICITY IN PROPERTIES:
When elements are arranged in the increasing of atomic number , elements having similar properties recur at regular intervals in the periodic table . This type of property is called Periodicity.

CAUSE OF PERIODICITY:
(1) The cause of Periodicity in properties is due to the same outermist electronic coming at regular time intervals.
(2) In the periodic table, elements with similar properties recure at intervals of 2, 8, 8, 18, 18, 32, and 32, these numbers are called as magic numbers.
[I]PERIODIC IN PHYSICAL PROPERTIES:
(1) ATOMIC DENSITY:
Density is the ratio of mass and volume. Higher the atomic volume leads to lower density as vice versa lower the atomic volume leads to higher density .
(A) Trends in group:
When we move top to bottom in a group the atomic density generally increases , it is due to increasing in atomic volume and atomic mass because too to bottom in group , number of shells increases but mass is more and more increases with respect to volume, so finally the atomic density ina group increases.
(B) Trends in period: 
When we move from left to right along with a period , the atomic density increases and become maximum at mid period , and after that decrease.
(C) Atomic density depends upon two factors these are given as.
(i) the electronic configuration of inner most shells
(ii) packing capacity 
EXCEPTION:
(1) Density of Na > Density of K
Reason: 
The density of 'Na' is greater than the density of of 'K' .It is due to the inner shells of 'Na' atom is fully filled but the shells the inner most shells of 'K' not full filled.
11Na= 1s2 2s2 2p6 3s1 (Completely filled Inner shell s)
19K= 1s2 2s2 2p6 3s1 3p6 3d0, 4s1 (incomplete inner shells)
(2) Density of Mg > Density of Ca 
Reason:
The density of 'Mg' is greater than the density of of 'Ca' .It is due to the inner shells of 'Mg' atom is fully filled but the shells the inner most shells of 'Ca' not full filled.
12Mg= 1s2 2s2 2p6 3s2 (Completely filled Inner shell s)
20Ca= 1s2 2s2 2p6 3s1 3p6 3d0, 4s2 (incomplete inner shells)

(2) ATOMIC VOLUME:
Atomic Volume of is define as the volume occupied by one mole of atoms or gram atom of the given element in the solid state .
Thus Atomic volume = atomic weight in gram/ Density in solid state 
(A) In general atomic volume generally leads to higher density as vice versa higher atomic volume generally leads to lower density. 
(B) Trends in group:
When we move from top to bottom in a group the atomic volume generally increases.
(C) Trends in period: 
When we move from move left to right along a period the atomic volume first decrease to minimum at mid period then increases.

(3) MELTING AND BOILING POINT:
(A) Melting point: The temperature at which  a solid material changes into the liquid material is called melting point and process is called melting.
(B) Boiling point the temperature at a liquid material changes into its vapour is called boiling point and the process is called boiling. 
(C) Lower atomic volume generally leads to higher density , increases hardness and brittleness, less malleability and ductility.
(D) Trends in groups: 
1- When we move top to bottom in group of S-Block, the melting point and boiling point decrease.
2- When we move top to bottom in all group of d-Block, the melting point and boiling point increases.
 3- While we move IIIA TO VIA Groups , the MP and BP decreases.
 4- While we move VA TO VIIA Groups , the MP and BP increases.
(E) Trends in period: 
When we move from left to right through periodic table the value of MP and BP first increases to maximum after decrease like density.
(4) VALECNCY:
(5) SCREANING OR SHIELDING EFFECT:
(6) ATOMIC RADIUS:
(A) Type atomic radius:
(6.1) Covalent radius:
(6.2) Ionic radius:
(6.3) Vander waal's radius:It is define as half of the distance between nuclei of the two adjacent atom bonded with Vander waal's forces.
(1) The Vander waal's radius defined the atomic radius of inert gases.
(2) Vander waal's redius is greater than that of all known radius.
(3)Vander waal's radius is generally two times of Covalent radius.
(4) Vander waal's force is directly proportional to the molecular weight.
(6.4) Metallic radius:It is defined as half of the inter nuclear distance between the nucleus of two adjacent atoms in the metallic lattice . Metallic radius is greater than Covalent radius.
(B) Facter's affecting  atomic radii:
(1) Nuclear attraction:
(2) principle quantum number:
(3) Screaning effect:
(4) Multiplicity of bond
(5) % S Character:
(C) Periodicity of atomic radius :
(1) In Group :when we move from top to bottom in group generally atomic radius increases as atomic number increases.this due to the addition of new energy shells increases, which overcome the effect of increased nuclear charge as results atomic radius gradually increase down the group.
(2) In Period : (A) When we move from left to right in group generally atomic radius decreases regularly in the representative elements because the principal quantum number remains same in period but the nuclear charge increases due to increased in nuclear charge the force of attraction towards nucleus increases, which brings contraction in size.
(B) In case of noble gas elements , the atomic radius increases exceptionally .It is due the fact that the noble gases have Vander waal's radius , which is always has higher value than Covalent radius.
(C) In case of transition elements , decrease in size is very less since the last or differentiating electrons of the elements into (n-1)d level . The additional electrons effectively screen much increased nuclear charge on the outer most  ns electrons therefore , size remains almost constant.

(7) IONIZATION POTENTIAL(IP)/ENTHALPY:
(A) Facter's affecting ionization enthalpy:
(1) Atomic radius :
(2) Screening effect:
(3) Nuclear charge:
(4) Penentration effect of electrons:
(5) Half filled and fully filled configuration:
(B) Periodicity in ionization enthalpy:
(1) In group:
(2) In period :
(C) Application of Ionization enthalpy:
(1) Metallic and non metallic Character:
(2) Reactivity:
(3) Reducing Capacity:
(4) Oxidising Capacity:
(5) Type of bond :

(8) ENECTRON GAIN ENTHALPY/ENTHALPY:

(A) Facter's affecting EGE:
(1) Atomic radius:
(2) Nuclear charge:
(3) Half filled and fully filled configuration:
(B) Periodicity in electron affinity:
(1) In Group:
(2) In period:
(9) ECTRONEGATIVITY:
(A) Facter's  affecting electronegativity:
(1) Nuclear attraction:
(2) Atomic radius:
(3) Oxidation state:
(4) % S Character:
(B) Periodicity in electronegativity:
(1) In groups:
(2) In periods:
(3) Reason:
(C) Applications of electronegativity:
(1) Metallic and non metallic character:
(2) Bond energy (BE) :
(3) Bond lenght (BL):The nature of bond between two atoms can be decided on basis of electronegativity difference between bonded atoms
(a) The difference between electronegativity of two bonded ago is zero then , the bond is purely covalent.
(b) The % ionic Character in covalent bond can be calculated by the Henny Smith equation:
   % Ionic Character=16 (Xa-Xb)+3.5(Xa-Xb)2
On the basis of this equation % ionic Character calculated as follows:
∆E=0     
(4) Nature of Bond :
(5) Nature of hydrides:
(5) Nature of hydroxide:
(6) Nature of Oxides:
(D) Measurement of electronegativity:
(1) Mulliken Scale: According to Mulliken's the electronegativity of an atom is the arithmetic mean of first ionization enthalpy and it's electron gain enthalpy 
(2) Pauling bond energy scale: this scale is based on the bond energies. According to Pauling, the the electronegativity difference XA-XB between two atom A and B is given by
XA-XB= 0.208[✓∆E]
Where ∆E =Resonance energy 
∆E=Actual bond energy(EA-B) -✓EA2-EB2

ILLUSTRATIVE EXAMPLE: The ionic resonance of C-H bond is 5.75 kcal. The electronegativity of hydrogen is 2.1 . What will be the electronegativity of carbon?
ILLUSTRATIVE EXAMPLE : The value of ionic resonance energy of AB molecule is 4 kcal. The electronegativity of B is 2 . The electronegativity of A is :

(3) Relation between Mulliken and Pauling:
(4) Allred Roshow Scale:
(5) Relation between Allred Roshow and Pauling :


[II] PERIODICITY IN CHEMICAL PROPERTIES:

[III] PERIODICITY IN CHEMICAL REACTIVITY:







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