Important Classification of Elements & Periodicity in Properties Formulas for JEE and NEET

 Page 1


  
INORGANIC CHEMISTRY
PERIODIC TABLE & PERIODICITY
Development of Modern Periodic Table :
(a) Dobereiner?s  Triads : He arranged similar elements in the groups of
three elements called as triads
(b) Newland?s Law of Octave : He was the first to correlate the chemical
properties of the elements with their atomic masses.
(c) Lother Meyer?s Classification : He plotted a graph between atomic
masses against their respective  atomic volumes  for a number of elements.
He found the 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 and
(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 the periodic functions of their atomic masses.
(d) Mendeleev?s Periodic Table :
Mendeleev?s Periodic?s Law
the physical and chemical properties of the elements are the periodic
functions of their atomic masses.
Periods Number of  Elements Called as
(1)
st
 n = 1 2 Very short period
(2)
nd
 n = 2 8 Short period
(3)
rd
 n = 3 8 Short period
(4)
th
 n = 4 18 Long period
(5)
th
 n = 5 18 Long period
(6)
th
 n = 6 32 Very long period
(7)
th
 n = 7 19 Incomplete period
Merits of  Mendeleev?s Periodic table:
? It has simplified and systematised the study of elements and
their compounds.
? It has helped in predicting the discovery of new elements on the
basis of the blank spaces given in its periodic table.
Page 2


  
INORGANIC CHEMISTRY
PERIODIC TABLE & PERIODICITY
Development of Modern Periodic Table :
(a) Dobereiner?s  Triads : He arranged similar elements in the groups of
three elements called as triads
(b) Newland?s Law of Octave : He was the first to correlate the chemical
properties of the elements with their atomic masses.
(c) Lother Meyer?s Classification : He plotted a graph between atomic
masses against their respective  atomic volumes  for a number of elements.
He found the 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 and
(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 the periodic functions of their atomic masses.
(d) Mendeleev?s Periodic Table :
Mendeleev?s Periodic?s Law
the physical and chemical properties of the elements are the periodic
functions of their atomic masses.
Periods Number of  Elements Called as
(1)
st
 n = 1 2 Very short period
(2)
nd
 n = 2 8 Short period
(3)
rd
 n = 3 8 Short period
(4)
th
 n = 4 18 Long period
(5)
th
 n = 5 18 Long period
(6)
th
 n = 6 32 Very long period
(7)
th
 n = 7 19 Incomplete period
Merits of  Mendeleev?s Periodic table:
? It has simplified and systematised the study of elements and
their compounds.
? It has helped in predicting the discovery of new elements on the
basis of the blank spaces given in its periodic table.
  
Demerits in Mendeleev?s Periodic Table :
? Position of hydrogen is uncertain .It has been placed in lA and VIIA groups
? No separate positions were  given to isotopes.
? Anomalous positions of lanthanides and actinides in periodic table.
? Order of increasing atomic weights is not strictly followed in the arrangement
of elements in the periodic table.
? Similar elements were placed in different groups.
? It didn?t explained the cause of periodicity.
(e) Long form of the Periodic Table or Moseley?s Periodic Table :
MODERN  PERIODIC LAW (MOSELEY?S PERIODIC LAW) :
If the elements are arranged in order of their increasing atomic number,
after a regular interval, elements 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 PERIODICITY :
The periodic repetition  of the properties of the elements is due to the
recurrence of similar valence shell electronic configurations after certain
regular intervals.
The modern periodic table consists of horizontal rows (periods) and vertical
column (groups).
Periods :
There are seven periods numbered as 1, 2, 3, 4, 5, 6 and 7.
? Each period consists of a series of elements having same valence shell.
? Each period corresponds to a particular principal quantum number of the
valence shell present in it.
? Each period  starts with an alkali metal having  outermost electronic
configuration as ns
1
.
? Each period ends with a noble gas with  outermost  electronic configuration
ns
2
np
6
 except  helium having  outermost electronic configuration as 1s
2
.
? Each period starts with  the filling of new energy level.
? The number of elements in each period is twice the number of atomic
orbitals available in energy level that is being filled.
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.
Page 3


  
INORGANIC CHEMISTRY
PERIODIC TABLE & PERIODICITY
Development of Modern Periodic Table :
(a) Dobereiner?s  Triads : He arranged similar elements in the groups of
three elements called as triads
(b) Newland?s Law of Octave : He was the first to correlate the chemical
properties of the elements with their atomic masses.
(c) Lother Meyer?s Classification : He plotted a graph between atomic
masses against their respective  atomic volumes  for a number of elements.
He found the 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 and
(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 the periodic functions of their atomic masses.
(d) Mendeleev?s Periodic Table :
Mendeleev?s Periodic?s Law
the physical and chemical properties of the elements are the periodic
functions of their atomic masses.
Periods Number of  Elements Called as
(1)
st
 n = 1 2 Very short period
(2)
nd
 n = 2 8 Short period
(3)
rd
 n = 3 8 Short period
(4)
th
 n = 4 18 Long period
(5)
th
 n = 5 18 Long period
(6)
th
 n = 6 32 Very long period
(7)
th
 n = 7 19 Incomplete period
Merits of  Mendeleev?s Periodic table:
? It has simplified and systematised the study of elements and
their compounds.
? It has helped in predicting the discovery of new elements on the
basis of the blank spaces given in its periodic table.
  
Demerits in Mendeleev?s Periodic Table :
? Position of hydrogen is uncertain .It has been placed in lA and VIIA groups
? No separate positions were  given to isotopes.
? Anomalous positions of lanthanides and actinides in periodic table.
? Order of increasing atomic weights is not strictly followed in the arrangement
of elements in the periodic table.
? Similar elements were placed in different groups.
? It didn?t explained the cause of periodicity.
(e) Long form of the Periodic Table or Moseley?s Periodic Table :
MODERN  PERIODIC LAW (MOSELEY?S PERIODIC LAW) :
If the elements are arranged in order of their increasing atomic number,
after a regular interval, elements 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 PERIODICITY :
The periodic repetition  of the properties of the elements is due to the
recurrence of similar valence shell electronic configurations after certain
regular intervals.
The modern periodic table consists of horizontal rows (periods) and vertical
column (groups).
Periods :
There are seven periods numbered as 1, 2, 3, 4, 5, 6 and 7.
? Each period consists of a series of elements having same valence shell.
? Each period corresponds to a particular principal quantum number of the
valence shell present in it.
? Each period  starts with an alkali metal having  outermost electronic
configuration as ns
1
.
? Each period ends with a noble gas with  outermost  electronic configuration
ns
2
np
6
 except  helium having  outermost electronic configuration as 1s
2
.
? Each period starts with  the filling of new energy level.
? The number of elements in each period is twice the number of atomic
orbitals available in energy level that is being filled.
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.
Page 4


  
INORGANIC CHEMISTRY
PERIODIC TABLE & PERIODICITY
Development of Modern Periodic Table :
(a) Dobereiner?s  Triads : He arranged similar elements in the groups of
three elements called as triads
(b) Newland?s Law of Octave : He was the first to correlate the chemical
properties of the elements with their atomic masses.
(c) Lother Meyer?s Classification : He plotted a graph between atomic
masses against their respective  atomic volumes  for a number of elements.
He found the 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 and
(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 the periodic functions of their atomic masses.
(d) Mendeleev?s Periodic Table :
Mendeleev?s Periodic?s Law
the physical and chemical properties of the elements are the periodic
functions of their atomic masses.
Periods Number of  Elements Called as
(1)
st
 n = 1 2 Very short period
(2)
nd
 n = 2 8 Short period
(3)
rd
 n = 3 8 Short period
(4)
th
 n = 4 18 Long period
(5)
th
 n = 5 18 Long period
(6)
th
 n = 6 32 Very long period
(7)
th
 n = 7 19 Incomplete period
Merits of  Mendeleev?s Periodic table:
? It has simplified and systematised the study of elements and
their compounds.
? It has helped in predicting the discovery of new elements on the
basis of the blank spaces given in its periodic table.
  
Demerits in Mendeleev?s Periodic Table :
? Position of hydrogen is uncertain .It has been placed in lA and VIIA groups
? No separate positions were  given to isotopes.
? Anomalous positions of lanthanides and actinides in periodic table.
? Order of increasing atomic weights is not strictly followed in the arrangement
of elements in the periodic table.
? Similar elements were placed in different groups.
? It didn?t explained the cause of periodicity.
(e) Long form of the Periodic Table or Moseley?s Periodic Table :
MODERN  PERIODIC LAW (MOSELEY?S PERIODIC LAW) :
If the elements are arranged in order of their increasing atomic number,
after a regular interval, elements 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 PERIODICITY :
The periodic repetition  of the properties of the elements is due to the
recurrence of similar valence shell electronic configurations after certain
regular intervals.
The modern periodic table consists of horizontal rows (periods) and vertical
column (groups).
Periods :
There are seven periods numbered as 1, 2, 3, 4, 5, 6 and 7.
? Each period consists of a series of elements having same valence shell.
? Each period corresponds to a particular principal quantum number of the
valence shell present in it.
? Each period  starts with an alkali metal having  outermost electronic
configuration as ns
1
.
? Each period ends with a noble gas with  outermost  electronic configuration
ns
2
np
6
 except  helium having  outermost electronic configuration as 1s
2
.
? Each period starts with  the filling of new energy level.
? The number of elements in each period is twice the number of atomic
orbitals available in energy level that is being filled.
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.
  
CLASSIFICATION OF THE ELEMENTS :
(a) 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.
(b) p-Block Elements
Group 13 to 18 elements constitute the p-block. General electronic
configuration is [inert gas] ns
2 
np
1-6
(c) d-Block Elements
Group 3 to 12 elements constitute the d-block. General electronic
configuration is [inert gas] (n ? 1) d
1-10
 ns
1-2
(d) f-Block Elements
General electronic configuration is (n ? 2) f
1-14
 (n ? 1) d
0-1
 ns
2
. All f-block
elements belong to 3
rd
 group.
Elements of f-blocks have been classified into two series. (1) ?
st
 inner
transition or 4 f-series, contains 14 elements  
58
Ce to 
71
Lu. (2). IInd inner
transition or 5 f-series, contains 14 elements  
90
Th to 
103
Lr.
Prediction of period, group and block :
? Period of an element corresponds to the principal quantum number of the
valence shell.
? The block of an element corresponds to the type of subshell which receives
the last electron.
? The group is predicted from the number of electrons in the valence shell
or/and penultimate shell as follows.
(a) For s-block elements ; Group no. = the no. of valence electrons
(b) For p-block elements ; Group no. = 10 + no. of valence electrons
(c) For d-block elements ; Group no. = no. of electrons in (n ? 1) d sub shell
+ no. of electrons in valence shell.
Metals and nonmetals :
? The metals are characterised by their nature of readily giving up the
electron(s) and from shinning lustre. Metals comprises more than 78% of
all known elements and appear on the left hand side of the periodic table.
Metals are usually solids at room temperature (except mercury, gallium).
They have high melting and boiling points and are good conductors of heat
and electricity. Oxides of metals are generally basic in nature (some metals
in their higher oxidation state form acid oxides e.g. CrO
3
).
Page 5


  
INORGANIC CHEMISTRY
PERIODIC TABLE & PERIODICITY
Development of Modern Periodic Table :
(a) Dobereiner?s  Triads : He arranged similar elements in the groups of
three elements called as triads
(b) Newland?s Law of Octave : He was the first to correlate the chemical
properties of the elements with their atomic masses.
(c) Lother Meyer?s Classification : He plotted a graph between atomic
masses against their respective  atomic volumes  for a number of elements.
He found the 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 and
(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 the periodic functions of their atomic masses.
(d) Mendeleev?s Periodic Table :
Mendeleev?s Periodic?s Law
the physical and chemical properties of the elements are the periodic
functions of their atomic masses.
Periods Number of  Elements Called as
(1)
st
 n = 1 2 Very short period
(2)
nd
 n = 2 8 Short period
(3)
rd
 n = 3 8 Short period
(4)
th
 n = 4 18 Long period
(5)
th
 n = 5 18 Long period
(6)
th
 n = 6 32 Very long period
(7)
th
 n = 7 19 Incomplete period
Merits of  Mendeleev?s Periodic table:
? It has simplified and systematised the study of elements and
their compounds.
? It has helped in predicting the discovery of new elements on the
basis of the blank spaces given in its periodic table.
  
Demerits in Mendeleev?s Periodic Table :
? Position of hydrogen is uncertain .It has been placed in lA and VIIA groups
? No separate positions were  given to isotopes.
? Anomalous positions of lanthanides and actinides in periodic table.
? Order of increasing atomic weights is not strictly followed in the arrangement
of elements in the periodic table.
? Similar elements were placed in different groups.
? It didn?t explained the cause of periodicity.
(e) Long form of the Periodic Table or Moseley?s Periodic Table :
MODERN  PERIODIC LAW (MOSELEY?S PERIODIC LAW) :
If the elements are arranged in order of their increasing atomic number,
after a regular interval, elements 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 PERIODICITY :
The periodic repetition  of the properties of the elements is due to the
recurrence of similar valence shell electronic configurations after certain
regular intervals.
The modern periodic table consists of horizontal rows (periods) and vertical
column (groups).
Periods :
There are seven periods numbered as 1, 2, 3, 4, 5, 6 and 7.
? Each period consists of a series of elements having same valence shell.
? Each period corresponds to a particular principal quantum number of the
valence shell present in it.
? Each period  starts with an alkali metal having  outermost electronic
configuration as ns
1
.
? Each period ends with a noble gas with  outermost  electronic configuration
ns
2
np
6
 except  helium having  outermost electronic configuration as 1s
2
.
? Each period starts with  the filling of new energy level.
? The number of elements in each period is twice the number of atomic
orbitals available in energy level that is being filled.
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.
  
CLASSIFICATION OF THE ELEMENTS :
(a) 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.
(b) p-Block Elements
Group 13 to 18 elements constitute the p-block. General electronic
configuration is [inert gas] ns
2 
np
1-6
(c) d-Block Elements
Group 3 to 12 elements constitute the d-block. General electronic
configuration is [inert gas] (n ? 1) d
1-10
 ns
1-2
(d) f-Block Elements
General electronic configuration is (n ? 2) f
1-14
 (n ? 1) d
0-1
 ns
2
. All f-block
elements belong to 3
rd
 group.
Elements of f-blocks have been classified into two series. (1) ?
st
 inner
transition or 4 f-series, contains 14 elements  
58
Ce to 
71
Lu. (2). IInd inner
transition or 5 f-series, contains 14 elements  
90
Th to 
103
Lr.
Prediction of period, group and block :
? Period of an element corresponds to the principal quantum number of the
valence shell.
? The block of an element corresponds to the type of subshell which receives
the last electron.
? The group is predicted from the number of electrons in the valence shell
or/and penultimate shell as follows.
(a) For s-block elements ; Group no. = the no. of valence electrons
(b) For p-block elements ; Group no. = 10 + no. of valence electrons
(c) For d-block elements ; Group no. = no. of electrons in (n ? 1) d sub shell
+ no. of electrons in valence shell.
Metals and nonmetals :
? The metals are characterised by their nature of readily giving up the
electron(s) and from shinning lustre. Metals comprises more than 78% of
all known elements and appear on the left hand side of the periodic table.
Metals are usually solids at room temperature (except mercury, gallium).
They have high melting and boiling points and are good conductors of heat
and electricity. Oxides of metals are generally basic in nature (some metals
in their higher oxidation state form acid oxides e.g. CrO
3
).
  
? Nonmetals do not lose electrons but take up electrons to form corresponding
anions. Nonmetals are located at the top right hand side of the periodic
table. Nonmetals are usually solids, liquids  or gases at room temperature
with low melting and boiling points. They are poor conductors of heat and
electricity. Oxides of nonmetals are generally acidic in nature.
Metalloids (Semi metals) :
The metalloids comprise of the elements B, Si, Ge, As, Sb and Te.
Diagonal relationship :
2
nd
 period Li Be B C
          
3
rd
 period Na Mg Al Si
Diagonal relationship arises because of ;
(i) on descending a group, the atoms and ions increase in size. On
moving from left to right in the periodic table, the size decreases.
Thus on moving diagonally, the size remains nearly the same.
(Li = 1.23 Å & Mg = 1.36 Å ; Li
+
 = 0.76 Å & Mg
2+
 = 0.72 Å)
(ii) it is sometimes suggested that the diagonal relationship arises because
of diagonal similarity in electronegativity values.
(Li = 1.0 & Mg = 1.2 ; Be = 1.5 & Al = 1.5 ; B = 2.0 & Si = 1.8)
The periodicity of atomic properties :
(i) Effective nuclear charge :
The effective nuclear charge (Z
eff
) = Z ? ?, (where Z is the actual nuclear
charge (atomic number of the element) and ? is the shielding (screening)
constant). The value of ? i.e. shielding effect can be determined using the
Slater?s rules.
(ii) Atomic radius :
(A) Covalent radius : It is one-half of the distance between the centres of
two nuclei (of like atoms) bonded by a single covalent bond. Covalent
radius is generally used for nonmetals.
(B) Vander Waal?s radius (Collision radius) : It is one-half of the internuclear
distance between two adjacent atoms in two nearest neighbouring
molecules of the substance in solid state.
(C) Metallic radius (Crystal radius) :
It is one-half of the distance between the nuclei of two adjacent metal atoms in
the metallic crystal lattice.
? Thus, the covalent, vander Wall?s and metallic radius magnitude wise follows
the order,
r
covalent
 < r
crystal
 < r
vander Walls