Periodic Properties JEE Notes | EduRev

JEE : Periodic Properties JEE Notes | EduRev

 Page 1


Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
1
www.learnershabitat.ac.in
PERIODIC PROPERTIES
PERIODIC TABLE PERIODIC TABLE
GROUPS PERIODS Ionisation
energy
Electron
affinity
Electro
negativity
Radii Lanthanide
Contraction
Metallic
Character
Old convention IA   IIA   IIIB   IVB   VB   VIB   VIIB              VIII         IB   IIB    IIIA   IVA   VA   VIA   VIIA     0  
New convention 1    2    3     4     5      6      7      8       9      10    11   12      13     14   15   16     17   18  
    
                    
 
       
 
           
             
                 
              
                      
                    
        
   
       S– Block p - Block 
      
H He
Li   Be B     C     N    O     F   Ne
 d -  Block 
  Na Mg                         Al    Si    P   S     Cl    Ar  
K   Ca  Sc    Ti      V    Cr   Mn   Fe    Co    Ni    Cu    Zn  Ga   Ge   As   Se   Br   Kr 
Rb   Sr   Y    Zr   Nb   Mo Tc    Ru    Rh   Pd   Ag  Cd   In    Sn   Sb  Te    I   Xe
Cs  Ba   La  Hf    Ta  W    Re   Os     Ir     Pt    Au    Hg   Tl    Pb  Bi   Po  At  Rn
 
 Fr  Ra  Ac   
             
               
   
*   
**
1
2
3
4
5
6
7
 f-Block 
? Helium  belongs to s-block because last entered electron goes in s-block.
? Iridium  is the most dense element followed by Osmium.
? NOTE : (1) Last entered electron (According to Aufbau’s Principle) decides the block of the element.
(2). The valence shell determines the period number.
GENERAL PROPERTIES OF PERIODIC TABLE
(1) There are Seventeen non-metals (including hydrogen) in periodic table.
(2) Five non - metals are solid C, P, S, Se, I.
(3) One non - metal is liquid i.e. Br.
(4) Eleven non-metals are gaseous.
PERIODIC PROPERTIES
PERIODIC PROPERTIES
Page 2


Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
1
www.learnershabitat.ac.in
PERIODIC PROPERTIES
PERIODIC TABLE PERIODIC TABLE
GROUPS PERIODS Ionisation
energy
Electron
affinity
Electro
negativity
Radii Lanthanide
Contraction
Metallic
Character
Old convention IA   IIA   IIIB   IVB   VB   VIB   VIIB              VIII         IB   IIB    IIIA   IVA   VA   VIA   VIIA     0  
New convention 1    2    3     4     5      6      7      8       9      10    11   12      13     14   15   16     17   18  
    
                    
 
       
 
           
             
                 
              
                      
                    
        
   
       S– Block p - Block 
      
H He
Li   Be B     C     N    O     F   Ne
 d -  Block 
  Na Mg                         Al    Si    P   S     Cl    Ar  
K   Ca  Sc    Ti      V    Cr   Mn   Fe    Co    Ni    Cu    Zn  Ga   Ge   As   Se   Br   Kr 
Rb   Sr   Y    Zr   Nb   Mo Tc    Ru    Rh   Pd   Ag  Cd   In    Sn   Sb  Te    I   Xe
Cs  Ba   La  Hf    Ta  W    Re   Os     Ir     Pt    Au    Hg   Tl    Pb  Bi   Po  At  Rn
 
 Fr  Ra  Ac   
             
               
   
*   
**
1
2
3
4
5
6
7
 f-Block 
? Helium  belongs to s-block because last entered electron goes in s-block.
? Iridium  is the most dense element followed by Osmium.
? NOTE : (1) Last entered electron (According to Aufbau’s Principle) decides the block of the element.
(2). The valence shell determines the period number.
GENERAL PROPERTIES OF PERIODIC TABLE
(1) There are Seventeen non-metals (including hydrogen) in periodic table.
(2) Five non - metals are solid C, P, S, Se, I.
(3) One non - metal is liquid i.e. Br.
(4) Eleven non-metals are gaseous.
PERIODIC PROPERTIES
PERIODIC PROPERTIES
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
2
www.learnershabitat.ac.in
(5) Six gases are monoatomic (noble gases) i.e. He, Ne, Ar, Kr, Xe, Rn.
(6) Five gases are diatomic, they are H, F, N, O, Cl
(7) There are eight metalloids in periodic table like, B, Si, Ge, As, Sb, Te, Po, At.
(8) Five elements are liquid at room temperature namely Cs, Fr, Ga, Hg, and Br,
(9) s - Block and p - Block together are called Representative elements.
(10) Five elements are radioactive amongst representative elements. They are Po, At, Rn, Fr and Ra
(11) There are seven periods in long - form of periodic table.
1.DEVELOPEMENT OF MODERN PERIODIC TABLE
Dobereiner's Triads :
He arranged similar elements in the groups of three elements called as triads, in which the atomic mass
of the central element was merely the arithmatic mean of atomic masses of other two elements or all
the three elements possessed nearly the same atomic masses
Li Na K
7 23 39 7 + 39/2 = 23
Fe Co Ni
55.85 58.93 58.71 nearly same atomic masses
It was restricted to few elements, therefore, discarded
NEWLAND'S LAW OF OCTAVES :
He was the first to correlate the chemical properties of the elements with their atomic masses.
According to him if the elements are arranged in the order of their increasing atomic masses the eighth
element starting from given one is similar in properties to the first one.
This arrangement of elements is called as Newland's law of Octave.
Li Be B C N O F
Ns Mg Al Si P S Cl
K Ca
This classification worked quite well for the ligher elements but it failed in case of heavier elements
and, therefore, discarded
LOTHER MEYER'S CLASSIFICATION
He determined the atomic volumes by dividing atomic mass with its density in solid states.
He ploted a graph between atomic masses against their respective atomic volumes for a number of
elements. He found the following observations.
(i) Elements with similar properties occupied similar positions on the curve.
(ii) Alkali metals having larger atomic volumes occupied the crests.
(iii) Transitions elements occupied the troughs.
(iv) The halogens occupied the ascending portions of the curve before the inert gases.
(v) Alkaline earth metals occupied the positions at about the mid points of the descending portions of
the curve.
On the basis of these observations he concluded that the atomic volumes (a physical property) of the
elements are a periodic function of their atomic masses.
It was discarded as it lacks practical utility.
Page 3


Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
1
www.learnershabitat.ac.in
PERIODIC PROPERTIES
PERIODIC TABLE PERIODIC TABLE
GROUPS PERIODS Ionisation
energy
Electron
affinity
Electro
negativity
Radii Lanthanide
Contraction
Metallic
Character
Old convention IA   IIA   IIIB   IVB   VB   VIB   VIIB              VIII         IB   IIB    IIIA   IVA   VA   VIA   VIIA     0  
New convention 1    2    3     4     5      6      7      8       9      10    11   12      13     14   15   16     17   18  
    
                    
 
       
 
           
             
                 
              
                      
                    
        
   
       S– Block p - Block 
      
H He
Li   Be B     C     N    O     F   Ne
 d -  Block 
  Na Mg                         Al    Si    P   S     Cl    Ar  
K   Ca  Sc    Ti      V    Cr   Mn   Fe    Co    Ni    Cu    Zn  Ga   Ge   As   Se   Br   Kr 
Rb   Sr   Y    Zr   Nb   Mo Tc    Ru    Rh   Pd   Ag  Cd   In    Sn   Sb  Te    I   Xe
Cs  Ba   La  Hf    Ta  W    Re   Os     Ir     Pt    Au    Hg   Tl    Pb  Bi   Po  At  Rn
 
 Fr  Ra  Ac   
             
               
   
*   
**
1
2
3
4
5
6
7
 f-Block 
? Helium  belongs to s-block because last entered electron goes in s-block.
? Iridium  is the most dense element followed by Osmium.
? NOTE : (1) Last entered electron (According to Aufbau’s Principle) decides the block of the element.
(2). The valence shell determines the period number.
GENERAL PROPERTIES OF PERIODIC TABLE
(1) There are Seventeen non-metals (including hydrogen) in periodic table.
(2) Five non - metals are solid C, P, S, Se, I.
(3) One non - metal is liquid i.e. Br.
(4) Eleven non-metals are gaseous.
PERIODIC PROPERTIES
PERIODIC PROPERTIES
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
2
www.learnershabitat.ac.in
(5) Six gases are monoatomic (noble gases) i.e. He, Ne, Ar, Kr, Xe, Rn.
(6) Five gases are diatomic, they are H, F, N, O, Cl
(7) There are eight metalloids in periodic table like, B, Si, Ge, As, Sb, Te, Po, At.
(8) Five elements are liquid at room temperature namely Cs, Fr, Ga, Hg, and Br,
(9) s - Block and p - Block together are called Representative elements.
(10) Five elements are radioactive amongst representative elements. They are Po, At, Rn, Fr and Ra
(11) There are seven periods in long - form of periodic table.
1.DEVELOPEMENT OF MODERN PERIODIC TABLE
Dobereiner's Triads :
He arranged similar elements in the groups of three elements called as triads, in which the atomic mass
of the central element was merely the arithmatic mean of atomic masses of other two elements or all
the three elements possessed nearly the same atomic masses
Li Na K
7 23 39 7 + 39/2 = 23
Fe Co Ni
55.85 58.93 58.71 nearly same atomic masses
It was restricted to few elements, therefore, discarded
NEWLAND'S LAW OF OCTAVES :
He was the first to correlate the chemical properties of the elements with their atomic masses.
According to him if the elements are arranged in the order of their increasing atomic masses the eighth
element starting from given one is similar in properties to the first one.
This arrangement of elements is called as Newland's law of Octave.
Li Be B C N O F
Ns Mg Al Si P S Cl
K Ca
This classification worked quite well for the ligher elements but it failed in case of heavier elements
and, therefore, discarded
LOTHER MEYER'S CLASSIFICATION
He determined the atomic volumes by dividing atomic mass with its density in solid states.
He ploted a graph between atomic masses against their respective atomic volumes for a number of
elements. He found the following observations.
(i) Elements with similar properties occupied similar positions on the curve.
(ii) Alkali metals having larger atomic volumes occupied the crests.
(iii) Transitions elements occupied the troughs.
(iv) The halogens occupied the ascending portions of the curve before the inert gases.
(v) Alkaline earth metals occupied the positions at about the mid points of the descending portions of
the curve.
On the basis of these observations he concluded that the atomic volumes (a physical property) of the
elements are a periodic function of their atomic masses.
It was discarded as it lacks practical utility.
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
3
www.learnershabitat.ac.in
(d) Mendeleev's Periodic Table :
Mendeleev's Periodic's Law
According to him the physical and chemical properties ofthe elements are a periodic function oftheir
atomic masses. He arranged then known elements in order of their increasing atomic masses considering
the facts that elements with similar properties should fall in the same vertical columns and leaving out
blank spaces where necessary.
Merits of Mendeleev's Periodic table :
(i) It has simplified and systematised the study of \3lements and their compounds
(ii) It has helped in predicting the discovery of new elements on the basis of the blank spaces given in its
periodic table.
Mendeleevs predicted the properties of those missing elements from the known properties of the other
elements in the same group. Eka - Aluminium and Eka-silicon names were given for gallium and germanium
(not discovered at the time of mendeleevs). Properties predicted by Mendeleevs for these elements
and those found experimentally were almost similar.
(iii) Atomic weights of elements were corrected. Atomic weight of Be was calculated to be 3 × 4.5 = 13.5
by considering its valency 3, was correctly calculated considering its valency 2 (2 × 4.5 = 9)
Demerits In Mendeleev's Periodic Table:
(i) Position of hydrogen is uncertain .It has been placed in lAand VilA groups because of its resemblance
with both the groups.
(ii) No separate positions were given to isotopes.
(iii) Anomalous position of lanthanides and actinides in periodic table.
(iv) Order of increaseing atomic weights is not strictly followed in the arrangment of elements in the periodic
table. For e.g.-Ar(At.wt.39.94) is placed before K(39.08) and Te (127.6) is placed before I (126.9)
Page 4


Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
1
www.learnershabitat.ac.in
PERIODIC PROPERTIES
PERIODIC TABLE PERIODIC TABLE
GROUPS PERIODS Ionisation
energy
Electron
affinity
Electro
negativity
Radii Lanthanide
Contraction
Metallic
Character
Old convention IA   IIA   IIIB   IVB   VB   VIB   VIIB              VIII         IB   IIB    IIIA   IVA   VA   VIA   VIIA     0  
New convention 1    2    3     4     5      6      7      8       9      10    11   12      13     14   15   16     17   18  
    
                    
 
       
 
           
             
                 
              
                      
                    
        
   
       S– Block p - Block 
      
H He
Li   Be B     C     N    O     F   Ne
 d -  Block 
  Na Mg                         Al    Si    P   S     Cl    Ar  
K   Ca  Sc    Ti      V    Cr   Mn   Fe    Co    Ni    Cu    Zn  Ga   Ge   As   Se   Br   Kr 
Rb   Sr   Y    Zr   Nb   Mo Tc    Ru    Rh   Pd   Ag  Cd   In    Sn   Sb  Te    I   Xe
Cs  Ba   La  Hf    Ta  W    Re   Os     Ir     Pt    Au    Hg   Tl    Pb  Bi   Po  At  Rn
 
 Fr  Ra  Ac   
             
               
   
*   
**
1
2
3
4
5
6
7
 f-Block 
? Helium  belongs to s-block because last entered electron goes in s-block.
? Iridium  is the most dense element followed by Osmium.
? NOTE : (1) Last entered electron (According to Aufbau’s Principle) decides the block of the element.
(2). The valence shell determines the period number.
GENERAL PROPERTIES OF PERIODIC TABLE
(1) There are Seventeen non-metals (including hydrogen) in periodic table.
(2) Five non - metals are solid C, P, S, Se, I.
(3) One non - metal is liquid i.e. Br.
(4) Eleven non-metals are gaseous.
PERIODIC PROPERTIES
PERIODIC PROPERTIES
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
2
www.learnershabitat.ac.in
(5) Six gases are monoatomic (noble gases) i.e. He, Ne, Ar, Kr, Xe, Rn.
(6) Five gases are diatomic, they are H, F, N, O, Cl
(7) There are eight metalloids in periodic table like, B, Si, Ge, As, Sb, Te, Po, At.
(8) Five elements are liquid at room temperature namely Cs, Fr, Ga, Hg, and Br,
(9) s - Block and p - Block together are called Representative elements.
(10) Five elements are radioactive amongst representative elements. They are Po, At, Rn, Fr and Ra
(11) There are seven periods in long - form of periodic table.
1.DEVELOPEMENT OF MODERN PERIODIC TABLE
Dobereiner's Triads :
He arranged similar elements in the groups of three elements called as triads, in which the atomic mass
of the central element was merely the arithmatic mean of atomic masses of other two elements or all
the three elements possessed nearly the same atomic masses
Li Na K
7 23 39 7 + 39/2 = 23
Fe Co Ni
55.85 58.93 58.71 nearly same atomic masses
It was restricted to few elements, therefore, discarded
NEWLAND'S LAW OF OCTAVES :
He was the first to correlate the chemical properties of the elements with their atomic masses.
According to him if the elements are arranged in the order of their increasing atomic masses the eighth
element starting from given one is similar in properties to the first one.
This arrangement of elements is called as Newland's law of Octave.
Li Be B C N O F
Ns Mg Al Si P S Cl
K Ca
This classification worked quite well for the ligher elements but it failed in case of heavier elements
and, therefore, discarded
LOTHER MEYER'S CLASSIFICATION
He determined the atomic volumes by dividing atomic mass with its density in solid states.
He ploted a graph between atomic masses against their respective atomic volumes for a number of
elements. He found the following observations.
(i) Elements with similar properties occupied similar positions on the curve.
(ii) Alkali metals having larger atomic volumes occupied the crests.
(iii) Transitions elements occupied the troughs.
(iv) The halogens occupied the ascending portions of the curve before the inert gases.
(v) Alkaline earth metals occupied the positions at about the mid points of the descending portions of
the curve.
On the basis of these observations he concluded that the atomic volumes (a physical property) of the
elements are a periodic function of their atomic masses.
It was discarded as it lacks practical utility.
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
3
www.learnershabitat.ac.in
(d) Mendeleev's Periodic Table :
Mendeleev's Periodic's Law
According to him the physical and chemical properties ofthe elements are a periodic function oftheir
atomic masses. He arranged then known elements in order of their increasing atomic masses considering
the facts that elements with similar properties should fall in the same vertical columns and leaving out
blank spaces where necessary.
Merits of Mendeleev's Periodic table :
(i) It has simplified and systematised the study of \3lements and their compounds
(ii) It has helped in predicting the discovery of new elements on the basis of the blank spaces given in its
periodic table.
Mendeleevs predicted the properties of those missing elements from the known properties of the other
elements in the same group. Eka - Aluminium and Eka-silicon names were given for gallium and germanium
(not discovered at the time of mendeleevs). Properties predicted by Mendeleevs for these elements
and those found experimentally were almost similar.
(iii) Atomic weights of elements were corrected. Atomic weight of Be was calculated to be 3 × 4.5 = 13.5
by considering its valency 3, was correctly calculated considering its valency 2 (2 × 4.5 = 9)
Demerits In Mendeleev's Periodic Table:
(i) Position of hydrogen is uncertain .It has been placed in lAand VilA groups because of its resemblance
with both the groups.
(ii) No separate positions were given to isotopes.
(iii) Anomalous position of lanthanides and actinides in periodic table.
(iv) Order of increaseing atomic weights is not strictly followed in the arrangment of elements in the periodic
table. For e.g.-Ar(At.wt.39.94) is placed before K(39.08) and Te (127.6) is placed before I (126.9)
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
4
www.learnershabitat.ac.in
(v) Similar elements were placed in differents groups(CuIB and Hg IIB) and the elements with different
properties were placed in same groups(alkali metals IA and coinage metals IB)
(vi) It didn't explained the cause of periodicity.
LONG FORM OF THE PERIODIC TABLE OR MOSELEY'S PERIODIC TABLE
He studied (1909) the frequency of the X-ray produecd by the bombardment of a strong beam of
electrons on 'metal target. He found that the square root of the frequency of X-rays (
v
) is directly
proportional to number of effective nuclear charge (z) of metal i.e. to atomic number and not to atomic
mass of the atom of that metal.(as nuclear charge of metal atom is equal to atomic number)
i.e. (
v
) = a (z - b)
Where 'a' is the proportionality constant and 'b' is a constant for all the lines in a given series of X-rays.
Therefore, he, concluded that atomic number was a better fundamental property of an element than
its atomic weight He suggested that the atomic number (z) instead of atomic weight should be basis of
the classification of the elements.
Modern Periodic Law (Moseley's Periodic Law)
Physical and chemical properties of elements are the periodic functions of their atomic number.lf the
elements are arranged in order of their increasing atomic numper, after a regular interval ,element with
similar properties are repeated.
Periodicity
The repetition of the properties of elements after regular intervals when the elements are arranged in
the order of increasing atomic number is called periodicity.
Cause of Perlodlcty:
The periodic repetition of the properties of the elements is due to the recurrence of similar valence
shell electronic configuration after certain regular intervals. For example, alkail metals have same
electronic configuration ns
1
, therefore, have similar properties.
The long form of periodic table is the contribution of Range, Werner, Bohr and Bury
This table is also referred to as Bohr's table since it follows Bohr's scheme of the arrangements of
elements into four types based on electronic configuration of elements
The modern periodic table consits of horizontal rows (periods) and vertical column (groups)
Periods:
There are seven periods numbered as 1, 2,3,4,5,6 and 7.
(i) Each period consists of a series of elements haVing same valence shell.
(ii) Each period corresponds to a particular principal quantum number of the valence shell present in it.
(iii) Each period starts with an alkali metal having outermost electronic configuration ns
1
.
(iv) Each period ends with a noble gas with outermost electronic configuration ns
2
np
6
 except helium having
outermost electronic configuration 1s
2
.
(v) Each period starts with the filling of new energy level.
(vi) The number of elements in each period is twice the number of atomic orbitals available in energy level
that is being filled. To illustrate
1
st
 period shortest period having only two elements. Filling of electron takes place in the first energy
shell, for which,
n = 1, ?. = 0 (s-subshell) and m = O.
Only one orbital (1s) is available and thus it contains only two elements.
Page 5


Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
1
www.learnershabitat.ac.in
PERIODIC PROPERTIES
PERIODIC TABLE PERIODIC TABLE
GROUPS PERIODS Ionisation
energy
Electron
affinity
Electro
negativity
Radii Lanthanide
Contraction
Metallic
Character
Old convention IA   IIA   IIIB   IVB   VB   VIB   VIIB              VIII         IB   IIB    IIIA   IVA   VA   VIA   VIIA     0  
New convention 1    2    3     4     5      6      7      8       9      10    11   12      13     14   15   16     17   18  
    
                    
 
       
 
           
             
                 
              
                      
                    
        
   
       S– Block p - Block 
      
H He
Li   Be B     C     N    O     F   Ne
 d -  Block 
  Na Mg                         Al    Si    P   S     Cl    Ar  
K   Ca  Sc    Ti      V    Cr   Mn   Fe    Co    Ni    Cu    Zn  Ga   Ge   As   Se   Br   Kr 
Rb   Sr   Y    Zr   Nb   Mo Tc    Ru    Rh   Pd   Ag  Cd   In    Sn   Sb  Te    I   Xe
Cs  Ba   La  Hf    Ta  W    Re   Os     Ir     Pt    Au    Hg   Tl    Pb  Bi   Po  At  Rn
 
 Fr  Ra  Ac   
             
               
   
*   
**
1
2
3
4
5
6
7
 f-Block 
? Helium  belongs to s-block because last entered electron goes in s-block.
? Iridium  is the most dense element followed by Osmium.
? NOTE : (1) Last entered electron (According to Aufbau’s Principle) decides the block of the element.
(2). The valence shell determines the period number.
GENERAL PROPERTIES OF PERIODIC TABLE
(1) There are Seventeen non-metals (including hydrogen) in periodic table.
(2) Five non - metals are solid C, P, S, Se, I.
(3) One non - metal is liquid i.e. Br.
(4) Eleven non-metals are gaseous.
PERIODIC PROPERTIES
PERIODIC PROPERTIES
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
2
www.learnershabitat.ac.in
(5) Six gases are monoatomic (noble gases) i.e. He, Ne, Ar, Kr, Xe, Rn.
(6) Five gases are diatomic, they are H, F, N, O, Cl
(7) There are eight metalloids in periodic table like, B, Si, Ge, As, Sb, Te, Po, At.
(8) Five elements are liquid at room temperature namely Cs, Fr, Ga, Hg, and Br,
(9) s - Block and p - Block together are called Representative elements.
(10) Five elements are radioactive amongst representative elements. They are Po, At, Rn, Fr and Ra
(11) There are seven periods in long - form of periodic table.
1.DEVELOPEMENT OF MODERN PERIODIC TABLE
Dobereiner's Triads :
He arranged similar elements in the groups of three elements called as triads, in which the atomic mass
of the central element was merely the arithmatic mean of atomic masses of other two elements or all
the three elements possessed nearly the same atomic masses
Li Na K
7 23 39 7 + 39/2 = 23
Fe Co Ni
55.85 58.93 58.71 nearly same atomic masses
It was restricted to few elements, therefore, discarded
NEWLAND'S LAW OF OCTAVES :
He was the first to correlate the chemical properties of the elements with their atomic masses.
According to him if the elements are arranged in the order of their increasing atomic masses the eighth
element starting from given one is similar in properties to the first one.
This arrangement of elements is called as Newland's law of Octave.
Li Be B C N O F
Ns Mg Al Si P S Cl
K Ca
This classification worked quite well for the ligher elements but it failed in case of heavier elements
and, therefore, discarded
LOTHER MEYER'S CLASSIFICATION
He determined the atomic volumes by dividing atomic mass with its density in solid states.
He ploted a graph between atomic masses against their respective atomic volumes for a number of
elements. He found the following observations.
(i) Elements with similar properties occupied similar positions on the curve.
(ii) Alkali metals having larger atomic volumes occupied the crests.
(iii) Transitions elements occupied the troughs.
(iv) The halogens occupied the ascending portions of the curve before the inert gases.
(v) Alkaline earth metals occupied the positions at about the mid points of the descending portions of
the curve.
On the basis of these observations he concluded that the atomic volumes (a physical property) of the
elements are a periodic function of their atomic masses.
It was discarded as it lacks practical utility.
Periodic Properties – Nirmaan TYCRP
LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
3
www.learnershabitat.ac.in
(d) Mendeleev's Periodic Table :
Mendeleev's Periodic's Law
According to him the physical and chemical properties ofthe elements are a periodic function oftheir
atomic masses. He arranged then known elements in order of their increasing atomic masses considering
the facts that elements with similar properties should fall in the same vertical columns and leaving out
blank spaces where necessary.
Merits of Mendeleev's Periodic table :
(i) It has simplified and systematised the study of \3lements and their compounds
(ii) It has helped in predicting the discovery of new elements on the basis of the blank spaces given in its
periodic table.
Mendeleevs predicted the properties of those missing elements from the known properties of the other
elements in the same group. Eka - Aluminium and Eka-silicon names were given for gallium and germanium
(not discovered at the time of mendeleevs). Properties predicted by Mendeleevs for these elements
and those found experimentally were almost similar.
(iii) Atomic weights of elements were corrected. Atomic weight of Be was calculated to be 3 × 4.5 = 13.5
by considering its valency 3, was correctly calculated considering its valency 2 (2 × 4.5 = 9)
Demerits In Mendeleev's Periodic Table:
(i) Position of hydrogen is uncertain .It has been placed in lAand VilA groups because of its resemblance
with both the groups.
(ii) No separate positions were given to isotopes.
(iii) Anomalous position of lanthanides and actinides in periodic table.
(iv) Order of increaseing atomic weights is not strictly followed in the arrangment of elements in the periodic
table. For e.g.-Ar(At.wt.39.94) is placed before K(39.08) and Te (127.6) is placed before I (126.9)
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(v) Similar elements were placed in differents groups(CuIB and Hg IIB) and the elements with different
properties were placed in same groups(alkali metals IA and coinage metals IB)
(vi) It didn't explained the cause of periodicity.
LONG FORM OF THE PERIODIC TABLE OR MOSELEY'S PERIODIC TABLE
He studied (1909) the frequency of the X-ray produecd by the bombardment of a strong beam of
electrons on 'metal target. He found that the square root of the frequency of X-rays (
v
) is directly
proportional to number of effective nuclear charge (z) of metal i.e. to atomic number and not to atomic
mass of the atom of that metal.(as nuclear charge of metal atom is equal to atomic number)
i.e. (
v
) = a (z - b)
Where 'a' is the proportionality constant and 'b' is a constant for all the lines in a given series of X-rays.
Therefore, he, concluded that atomic number was a better fundamental property of an element than
its atomic weight He suggested that the atomic number (z) instead of atomic weight should be basis of
the classification of the elements.
Modern Periodic Law (Moseley's Periodic Law)
Physical and chemical properties of elements are the periodic functions of their atomic number.lf the
elements are arranged in order of their increasing atomic numper, after a regular interval ,element with
similar properties are repeated.
Periodicity
The repetition of the properties of elements after regular intervals when the elements are arranged in
the order of increasing atomic number is called periodicity.
Cause of Perlodlcty:
The periodic repetition of the properties of the elements is due to the recurrence of similar valence
shell electronic configuration after certain regular intervals. For example, alkail metals have same
electronic configuration ns
1
, therefore, have similar properties.
The long form of periodic table is the contribution of Range, Werner, Bohr and Bury
This table is also referred to as Bohr's table since it follows Bohr's scheme of the arrangements of
elements into four types based on electronic configuration of elements
The modern periodic table consits of horizontal rows (periods) and vertical column (groups)
Periods:
There are seven periods numbered as 1, 2,3,4,5,6 and 7.
(i) Each period consists of a series of elements haVing same valence shell.
(ii) Each period corresponds to a particular principal quantum number of the valence shell present in it.
(iii) Each period starts with an alkali metal having outermost electronic configuration ns
1
.
(iv) Each period ends with a noble gas with outermost electronic configuration ns
2
np
6
 except helium having
outermost electronic configuration 1s
2
.
(v) Each period starts with the filling of new energy level.
(vi) The number of elements in each period is twice the number of atomic orbitals available in energy level
that is being filled. To illustrate
1
st
 period shortest period having only two elements. Filling of electron takes place in the first energy
shell, for which,
n = 1, ?. = 0 (s-subshell) and m = O.
Only one orbital (1s) is available and thus it contains only two elements.
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LEARNERS HABITAT EXPERTS Pvt. Ltd.: 97/1, IIIrd Floor, Near NCERT, Adchini, New Delhi, 011-32044009
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3
rd
 period short period having only eight elements. Filling of electrons takes place in the third energy
level. For which,
n = 3, ?. = 0, 1,2 and no. of orbitals m = 0, 3, 5
no. of orbitals       1 3 5
     (3s) (3p) (3d)
 ________________________
Total no. of orbitals 9
 ________________________
But the energy of 3d orbitals are higher than 4s orbitals. Therefore, four orbitals (one 3s and three 3p
orbitals) corresponding to n = 3 are filled before filling in 4s orbital (next energy elevel). Hence 3rd
period contains eight elements not eighteen elements.
Groups:
There are eighteen groups numbered as 1,2,3,4,5, ................ 13, 14, 15, 16, 17, 18.
Group consists of a series of elements having similar valence shell electronic configuration.
 
2. CLASSIFICATION OF THE ELEMENTS :
It is based on the type of orbitals which receives the differentiating electron (i.e., last electron).
s-block elements
When shells upto (n - 1) are completely filled and the last electron enters the s-orbital of the
outermost (nth) shell, the elements of this class are called s-block elements.
• Group 1 & 2 elements constitute the s-block.
• General electronic configuration is [inert gas] ns
1-2
• s-block elements lie on the extreme left of the periodic table.
• This block includes metals.
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