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) Effective Nuclear charge (Z* or Zeff):
(7)
Atomic Radius:
(8) Ionisation potential(Ip)/ Enthalpy:
(9) Electronegativity:
[II] Periodicity in chemical properties:
[III] Periodicity in chemical reactivity:
[IV] Some Important fact about elements of periodic
table.
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 top to bottom in group, number of shells
increases but mass is more and more increases with respect to volume, so
finally the atomic density in a 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 '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] Valency:
[5] Screening 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] Electron 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] Electronegativity:
(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:
