Concept - d & f - block Elements Class 12 Notes | EduRev

Class 12 : Concept - d & f - block Elements Class 12 Notes | EduRev

 Page 1


 1
Class XII: Chemistry 
Chapter 8: The d and f-Block Elements 
Top Concepts 
1. d -Block elements: The elements lying in the middle of periodic table 
belonging to groups 3 to 12 are known as d – block elements. Their 
general electronic configuration is (n – 1)d
1-10
 ns
1-2
 where (n – 1) 
stands for penultimate (last but one) shell.
 
2. Transition element: A transition element is defined as the one which 
has incompletely filled d orbitals in its ground state or in any one of its 
oxidation states.
 
3. Zinc, cadmium, mercury are not regarded as transition metals due to 
completely filled d – orbital. 
 
4. f-Block elements: The elements constituting the f -block are those in 
which the 4 f and 5 f orbitals are progressively filled in the latter two 
long periods.
 
5. Lanthanoids: The 14 elements immediately following lanthanum, i.e., 
Cerium (58) to Lutetium (71) are called lanthanoids. They belong to 
first inner transition series. Lanthanum (57) has similar properties. 
Therefore, it is studied along with lanthanoids.
 
6. Actinoids: The 14 elements immediately following actinium (89), with 
atomic numbers 90 (Thorium) to 103 (Lawrencium) are called 
actinoids. They belong to second inner transition series. Actinium (89) 
has similar properties. Therefore, it is studied along with actinoids.
 
7. Four transition series:
 
a. 3d – transition series. The transition elements with atomic 
number 21(Sc) to 30(Zn) and having incomplete 3d orbitals is called 
the first transition series. 
b. 4d – transition series. It consists of elements with atomic 
number 39(Y) to 48 (Cd) and having incomplete 4d orbitals. It is called 
second transition series. 
c. 5d – transition series. It consists of elements with atomic 
number 57(La), 72(Hf) to 80(Hg) having incomplete 5d orbitals. It is 
called third transition series. 
d. 6d – transition series. It consists of elements with atomic 
number 89(Ac), 104(Rf) to 112(Uub) having incomplete 6d orbitals. It 
is called fourth transition series. 
8. General Characteristics of transition elements: 
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Page 2


 1
Class XII: Chemistry 
Chapter 8: The d and f-Block Elements 
Top Concepts 
1. d -Block elements: The elements lying in the middle of periodic table 
belonging to groups 3 to 12 are known as d – block elements. Their 
general electronic configuration is (n – 1)d
1-10
 ns
1-2
 where (n – 1) 
stands for penultimate (last but one) shell.
 
2. Transition element: A transition element is defined as the one which 
has incompletely filled d orbitals in its ground state or in any one of its 
oxidation states.
 
3. Zinc, cadmium, mercury are not regarded as transition metals due to 
completely filled d – orbital. 
 
4. f-Block elements: The elements constituting the f -block are those in 
which the 4 f and 5 f orbitals are progressively filled in the latter two 
long periods.
 
5. Lanthanoids: The 14 elements immediately following lanthanum, i.e., 
Cerium (58) to Lutetium (71) are called lanthanoids. They belong to 
first inner transition series. Lanthanum (57) has similar properties. 
Therefore, it is studied along with lanthanoids.
 
6. Actinoids: The 14 elements immediately following actinium (89), with 
atomic numbers 90 (Thorium) to 103 (Lawrencium) are called 
actinoids. They belong to second inner transition series. Actinium (89) 
has similar properties. Therefore, it is studied along with actinoids.
 
7. Four transition series:
 
a. 3d – transition series. The transition elements with atomic 
number 21(Sc) to 30(Zn) and having incomplete 3d orbitals is called 
the first transition series. 
b. 4d – transition series. It consists of elements with atomic 
number 39(Y) to 48 (Cd) and having incomplete 4d orbitals. It is called 
second transition series. 
c. 5d – transition series. It consists of elements with atomic 
number 57(La), 72(Hf) to 80(Hg) having incomplete 5d orbitals. It is 
called third transition series. 
d. 6d – transition series. It consists of elements with atomic 
number 89(Ac), 104(Rf) to 112(Uub) having incomplete 6d orbitals. It 
is called fourth transition series. 
8. General Characteristics of transition elements: 
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a. Metallic character: All transition elements are metallic in nature, i.e. 
they have strong metallic bonds. This is because of presence of 
unpaired electrons. This gives rise to properties like high density, high 
enthalpies of atomization, and high melting and boiling points. 
b.  Atomic radii: The atomic radii decrease from Sc to Cr because the 
effective nuclear charge increases. The atomic size of Fe, Co, Ni is 
almost same because the attraction due to increase in nuclear charge 
is cancelled by the repulsion because of increase in shielding effect. Cu 
and Zn have bigger size because the shielding effect increases and 
electron electron repulsions repulsion increases.  
c. Lanthanoid Contraction: The steady decrease in the atomic and ionic 
radii of the transition metals as the atomic number increases. This is 
because of filling of 4f orbitals before the 5d orbitals. This contraction 
is size is quite regular. This is called lanthanoid contraction. It is 
because of lanthanoid contraction that the atomic radii of the second 
row of transition elements are almost similar to those of the third row 
of transition elements.  
d. Ionisation enthalpy: There is slight and irregular variation in ionization 
energies of transition metals due to irregular variation of atomic size. 
The I.E. of 5d transition series is higher than 3d and 4d transition 
series because of Lanthanoid Contraction. 
e. Oxidation state: Transition metals show variable oxidation states due 
to tendency of (n-1)d as well as ns electrons to take part in bond 
formation. 
f. Magnetic properties: Most of transition metals are paramagnetic in 
nature due to presence of unpaired electrons. It increase s from Sc to 
Cr and then decreases because number of unpaired and then decrease 
because number of unpaired electrons increases from Sc to Cr and 
then decreases. 
g. Catalytic properties: Most of transition metals are used as catalyst 
because of (i) presence of incomplete or empty d – orbitals, (ii) large 
surface area, (iii) varuable oxidation state, (iv) ability to form 
complexes, e.g., Fe, Ni, V
2
O
3
, Pt, Mo, Co and used as catalyst. 
h. Formation of coloured compounds: They form coloured ions due to 
presence of incompletely filled d – orbitals and unpaired electrons, 
they can undergo d – d transition by absorbing colour from visible 
region and radiating complementary colour. 
i. Formation of complexes: Transition metals form complexes due to (i) 
presence of vacant d – orbitals of suitable energy (ii) smaller size (iii) 
higher charge on cations. 
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 1
Class XII: Chemistry 
Chapter 8: The d and f-Block Elements 
Top Concepts 
1. d -Block elements: The elements lying in the middle of periodic table 
belonging to groups 3 to 12 are known as d – block elements. Their 
general electronic configuration is (n – 1)d
1-10
 ns
1-2
 where (n – 1) 
stands for penultimate (last but one) shell.
 
2. Transition element: A transition element is defined as the one which 
has incompletely filled d orbitals in its ground state or in any one of its 
oxidation states.
 
3. Zinc, cadmium, mercury are not regarded as transition metals due to 
completely filled d – orbital. 
 
4. f-Block elements: The elements constituting the f -block are those in 
which the 4 f and 5 f orbitals are progressively filled in the latter two 
long periods.
 
5. Lanthanoids: The 14 elements immediately following lanthanum, i.e., 
Cerium (58) to Lutetium (71) are called lanthanoids. They belong to 
first inner transition series. Lanthanum (57) has similar properties. 
Therefore, it is studied along with lanthanoids.
 
6. Actinoids: The 14 elements immediately following actinium (89), with 
atomic numbers 90 (Thorium) to 103 (Lawrencium) are called 
actinoids. They belong to second inner transition series. Actinium (89) 
has similar properties. Therefore, it is studied along with actinoids.
 
7. Four transition series:
 
a. 3d – transition series. The transition elements with atomic 
number 21(Sc) to 30(Zn) and having incomplete 3d orbitals is called 
the first transition series. 
b. 4d – transition series. It consists of elements with atomic 
number 39(Y) to 48 (Cd) and having incomplete 4d orbitals. It is called 
second transition series. 
c. 5d – transition series. It consists of elements with atomic 
number 57(La), 72(Hf) to 80(Hg) having incomplete 5d orbitals. It is 
called third transition series. 
d. 6d – transition series. It consists of elements with atomic 
number 89(Ac), 104(Rf) to 112(Uub) having incomplete 6d orbitals. It 
is called fourth transition series. 
8. General Characteristics of transition elements: 
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a. Metallic character: All transition elements are metallic in nature, i.e. 
they have strong metallic bonds. This is because of presence of 
unpaired electrons. This gives rise to properties like high density, high 
enthalpies of atomization, and high melting and boiling points. 
b.  Atomic radii: The atomic radii decrease from Sc to Cr because the 
effective nuclear charge increases. The atomic size of Fe, Co, Ni is 
almost same because the attraction due to increase in nuclear charge 
is cancelled by the repulsion because of increase in shielding effect. Cu 
and Zn have bigger size because the shielding effect increases and 
electron electron repulsions repulsion increases.  
c. Lanthanoid Contraction: The steady decrease in the atomic and ionic 
radii of the transition metals as the atomic number increases. This is 
because of filling of 4f orbitals before the 5d orbitals. This contraction 
is size is quite regular. This is called lanthanoid contraction. It is 
because of lanthanoid contraction that the atomic radii of the second 
row of transition elements are almost similar to those of the third row 
of transition elements.  
d. Ionisation enthalpy: There is slight and irregular variation in ionization 
energies of transition metals due to irregular variation of atomic size. 
The I.E. of 5d transition series is higher than 3d and 4d transition 
series because of Lanthanoid Contraction. 
e. Oxidation state: Transition metals show variable oxidation states due 
to tendency of (n-1)d as well as ns electrons to take part in bond 
formation. 
f. Magnetic properties: Most of transition metals are paramagnetic in 
nature due to presence of unpaired electrons. It increase s from Sc to 
Cr and then decreases because number of unpaired and then decrease 
because number of unpaired electrons increases from Sc to Cr and 
then decreases. 
g. Catalytic properties: Most of transition metals are used as catalyst 
because of (i) presence of incomplete or empty d – orbitals, (ii) large 
surface area, (iii) varuable oxidation state, (iv) ability to form 
complexes, e.g., Fe, Ni, V
2
O
3
, Pt, Mo, Co and used as catalyst. 
h. Formation of coloured compounds: They form coloured ions due to 
presence of incompletely filled d – orbitals and unpaired electrons, 
they can undergo d – d transition by absorbing colour from visible 
region and radiating complementary colour. 
i. Formation of complexes: Transition metals form complexes due to (i) 
presence of vacant d – orbitals of suitable energy (ii) smaller size (iii) 
higher charge on cations. 
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j. Interstitial compounds: Transition metals have voids or interstitials in 
which C, H, N, B etc. can fit into resulting in formation of interstitial 
compounds. They are non – stoichiometric, i.e., their composition is 
not fixed, e.g., steel. They are harder and less malleable and ductile. 
k. Alloys formation: They form alloys due to similar ionic size. Metals can 
replace each other in crystal lattice, e.g., brass, bronze, steel etc. 
9. Preparation of Potassium dichromate (K
2
Cr
2
O
7
): 
 It is prepared by fusion of chromate ore (FeCr
2
O
4
) with sodium 
carbonate in excess of air. 
 4FeCr
2
O
4
 + 8Na
2
CO
3
 + 7O
2
  ? ?? ? 8Na
2
CrO
4
 + 2Fe
2
O
3
 + 8CO
2
  
 2Na
2
CrO
4
 + H
2
SO
4
 ? ?? ? Na
2
Cr
2
O
7
 + H
2
O + Na
2
SO
4
 Sodium    Sodium 
 chromate    dichromate 
 Na
2
Cr
2
O
7
 + 2KCl ? ?? ? K
2
Cr
2
O
7
 + 2NaCl 
10. Effect of pH on chromate and dichromate ions: The chromates and 
dichromates are interconvertible in aqueous solution depending upon 
pH of the solution. The oxidation state of chromium in chromate and 
dichromate is the same. 
2 CrO
4
2-
 + 2H
+
 ? Cr
2
O
7
2-
 + H
2
O 
Cr
2
O
7
2-
 + 2 OH- ? 2 CrO
4
2-
+ H
2
O 
11. Potassium dichromate acts as a strong oxidizing agent in acidic 
medium. 
                 Cr
2
O
7
2-
 +14 H
+
 + 6e
-
 ? 2 Cr
3+
 + 7 H
2
O  
 
12. Preparation of Potassium permanganate (KMnO
4
): 
a.  Potassium permanganate is prepared by fusion of MnO
4
 with alkali 
metal hydroxide (KOH) in presence of O
2
 or oxidising agent like KNO
3
.  
It produces dark green K
2
MnO
4
 which undergoes oxidation as well as 
reduction in neutral or acidic solution to give permanganate. 
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Page 4


 1
Class XII: Chemistry 
Chapter 8: The d and f-Block Elements 
Top Concepts 
1. d -Block elements: The elements lying in the middle of periodic table 
belonging to groups 3 to 12 are known as d – block elements. Their 
general electronic configuration is (n – 1)d
1-10
 ns
1-2
 where (n – 1) 
stands for penultimate (last but one) shell.
 
2. Transition element: A transition element is defined as the one which 
has incompletely filled d orbitals in its ground state or in any one of its 
oxidation states.
 
3. Zinc, cadmium, mercury are not regarded as transition metals due to 
completely filled d – orbital. 
 
4. f-Block elements: The elements constituting the f -block are those in 
which the 4 f and 5 f orbitals are progressively filled in the latter two 
long periods.
 
5. Lanthanoids: The 14 elements immediately following lanthanum, i.e., 
Cerium (58) to Lutetium (71) are called lanthanoids. They belong to 
first inner transition series. Lanthanum (57) has similar properties. 
Therefore, it is studied along with lanthanoids.
 
6. Actinoids: The 14 elements immediately following actinium (89), with 
atomic numbers 90 (Thorium) to 103 (Lawrencium) are called 
actinoids. They belong to second inner transition series. Actinium (89) 
has similar properties. Therefore, it is studied along with actinoids.
 
7. Four transition series:
 
a. 3d – transition series. The transition elements with atomic 
number 21(Sc) to 30(Zn) and having incomplete 3d orbitals is called 
the first transition series. 
b. 4d – transition series. It consists of elements with atomic 
number 39(Y) to 48 (Cd) and having incomplete 4d orbitals. It is called 
second transition series. 
c. 5d – transition series. It consists of elements with atomic 
number 57(La), 72(Hf) to 80(Hg) having incomplete 5d orbitals. It is 
called third transition series. 
d. 6d – transition series. It consists of elements with atomic 
number 89(Ac), 104(Rf) to 112(Uub) having incomplete 6d orbitals. It 
is called fourth transition series. 
8. General Characteristics of transition elements: 
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a. Metallic character: All transition elements are metallic in nature, i.e. 
they have strong metallic bonds. This is because of presence of 
unpaired electrons. This gives rise to properties like high density, high 
enthalpies of atomization, and high melting and boiling points. 
b.  Atomic radii: The atomic radii decrease from Sc to Cr because the 
effective nuclear charge increases. The atomic size of Fe, Co, Ni is 
almost same because the attraction due to increase in nuclear charge 
is cancelled by the repulsion because of increase in shielding effect. Cu 
and Zn have bigger size because the shielding effect increases and 
electron electron repulsions repulsion increases.  
c. Lanthanoid Contraction: The steady decrease in the atomic and ionic 
radii of the transition metals as the atomic number increases. This is 
because of filling of 4f orbitals before the 5d orbitals. This contraction 
is size is quite regular. This is called lanthanoid contraction. It is 
because of lanthanoid contraction that the atomic radii of the second 
row of transition elements are almost similar to those of the third row 
of transition elements.  
d. Ionisation enthalpy: There is slight and irregular variation in ionization 
energies of transition metals due to irregular variation of atomic size. 
The I.E. of 5d transition series is higher than 3d and 4d transition 
series because of Lanthanoid Contraction. 
e. Oxidation state: Transition metals show variable oxidation states due 
to tendency of (n-1)d as well as ns electrons to take part in bond 
formation. 
f. Magnetic properties: Most of transition metals are paramagnetic in 
nature due to presence of unpaired electrons. It increase s from Sc to 
Cr and then decreases because number of unpaired and then decrease 
because number of unpaired electrons increases from Sc to Cr and 
then decreases. 
g. Catalytic properties: Most of transition metals are used as catalyst 
because of (i) presence of incomplete or empty d – orbitals, (ii) large 
surface area, (iii) varuable oxidation state, (iv) ability to form 
complexes, e.g., Fe, Ni, V
2
O
3
, Pt, Mo, Co and used as catalyst. 
h. Formation of coloured compounds: They form coloured ions due to 
presence of incompletely filled d – orbitals and unpaired electrons, 
they can undergo d – d transition by absorbing colour from visible 
region and radiating complementary colour. 
i. Formation of complexes: Transition metals form complexes due to (i) 
presence of vacant d – orbitals of suitable energy (ii) smaller size (iii) 
higher charge on cations. 
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j. Interstitial compounds: Transition metals have voids or interstitials in 
which C, H, N, B etc. can fit into resulting in formation of interstitial 
compounds. They are non – stoichiometric, i.e., their composition is 
not fixed, e.g., steel. They are harder and less malleable and ductile. 
k. Alloys formation: They form alloys due to similar ionic size. Metals can 
replace each other in crystal lattice, e.g., brass, bronze, steel etc. 
9. Preparation of Potassium dichromate (K
2
Cr
2
O
7
): 
 It is prepared by fusion of chromate ore (FeCr
2
O
4
) with sodium 
carbonate in excess of air. 
 4FeCr
2
O
4
 + 8Na
2
CO
3
 + 7O
2
  ? ?? ? 8Na
2
CrO
4
 + 2Fe
2
O
3
 + 8CO
2
  
 2Na
2
CrO
4
 + H
2
SO
4
 ? ?? ? Na
2
Cr
2
O
7
 + H
2
O + Na
2
SO
4
 Sodium    Sodium 
 chromate    dichromate 
 Na
2
Cr
2
O
7
 + 2KCl ? ?? ? K
2
Cr
2
O
7
 + 2NaCl 
10. Effect of pH on chromate and dichromate ions: The chromates and 
dichromates are interconvertible in aqueous solution depending upon 
pH of the solution. The oxidation state of chromium in chromate and 
dichromate is the same. 
2 CrO
4
2-
 + 2H
+
 ? Cr
2
O
7
2-
 + H
2
O 
Cr
2
O
7
2-
 + 2 OH- ? 2 CrO
4
2-
+ H
2
O 
11. Potassium dichromate acts as a strong oxidizing agent in acidic 
medium. 
                 Cr
2
O
7
2-
 +14 H
+
 + 6e
-
 ? 2 Cr
3+
 + 7 H
2
O  
 
12. Preparation of Potassium permanganate (KMnO
4
): 
a.  Potassium permanganate is prepared by fusion of MnO
4
 with alkali 
metal hydroxide (KOH) in presence of O
2
 or oxidising agent like KNO
3
.  
It produces dark green K
2
MnO
4
 which undergoes oxidation as well as 
reduction in neutral or acidic solution to give permanganate. 
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 4
  
22 24
2
442
2MnO 4KOH O 2K MnO 2H O
4H 3MnO 2MnO MnO 2H O
+- -
++ ????+
+????+ +
2
2
)
Or 
 Commercially it is prepared by the alkaline oxidative fusion of MnO
2
 
followed by the electrolytic oxidation of manganate (Vl). 
  
()
fused with KOH 2
24
in the presence of O or KNO
23
manganate ions
MnO MnO
-
? ? ?? ??? ?? ??? ? ?
  
() (
electrolytic oxidation in alkaline medium 2
44
Green P urple
MnO MnO
--
? ? ?? ?? ?? ?? ?? ? ?? ??
(ii) In laboratory, Mn²
+
 salt can be oxidized by peroxodisulphate ion to 
permanganate ion. 
 
2+ 2- 2
28 2 4 4
2Mn + 5S O +8H O 2MnO 10SO 16H
- -+
?? ??+ + 
13. Potassium permanganate acts as a strong oxidizing agent in acidic, 
neutral or faintly basic medium. 
 In acidic medium. 
 MnO
4
-
 + 8 H
+
 + 5 e
-
 ? Mn
2+
 + 4 H
2
O 
 In neutral or faintly basic medium, 
 MnO
4
-
 + 3 e
-
 + 2 H
2
O ? MnO
2
 + 4OH
-
14. Properties of Lanthanoids and Actinoids.  
 Lanthanoids Actinoids  
+3 oxidation state is most common 
along with +2 and +4 
Actiniods also show higher oxidation 
states such as +4, +5, +6 and +7. 
 
They are more reactive  
Except Promethium, they are non – 
radioactive. 
They are radioactive 
The magnetic properties of 
lanthanoids are less complex than 
actinoids. 
The magnetic properties of the 
actinoids are more complex than 
those of the lanthanoids 
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 1
Class XII: Chemistry 
Chapter 8: The d and f-Block Elements 
Top Concepts 
1. d -Block elements: The elements lying in the middle of periodic table 
belonging to groups 3 to 12 are known as d – block elements. Their 
general electronic configuration is (n – 1)d
1-10
 ns
1-2
 where (n – 1) 
stands for penultimate (last but one) shell.
 
2. Transition element: A transition element is defined as the one which 
has incompletely filled d orbitals in its ground state or in any one of its 
oxidation states.
 
3. Zinc, cadmium, mercury are not regarded as transition metals due to 
completely filled d – orbital. 
 
4. f-Block elements: The elements constituting the f -block are those in 
which the 4 f and 5 f orbitals are progressively filled in the latter two 
long periods.
 
5. Lanthanoids: The 14 elements immediately following lanthanum, i.e., 
Cerium (58) to Lutetium (71) are called lanthanoids. They belong to 
first inner transition series. Lanthanum (57) has similar properties. 
Therefore, it is studied along with lanthanoids.
 
6. Actinoids: The 14 elements immediately following actinium (89), with 
atomic numbers 90 (Thorium) to 103 (Lawrencium) are called 
actinoids. They belong to second inner transition series. Actinium (89) 
has similar properties. Therefore, it is studied along with actinoids.
 
7. Four transition series:
 
a. 3d – transition series. The transition elements with atomic 
number 21(Sc) to 30(Zn) and having incomplete 3d orbitals is called 
the first transition series. 
b. 4d – transition series. It consists of elements with atomic 
number 39(Y) to 48 (Cd) and having incomplete 4d orbitals. It is called 
second transition series. 
c. 5d – transition series. It consists of elements with atomic 
number 57(La), 72(Hf) to 80(Hg) having incomplete 5d orbitals. It is 
called third transition series. 
d. 6d – transition series. It consists of elements with atomic 
number 89(Ac), 104(Rf) to 112(Uub) having incomplete 6d orbitals. It 
is called fourth transition series. 
8. General Characteristics of transition elements: 
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a. Metallic character: All transition elements are metallic in nature, i.e. 
they have strong metallic bonds. This is because of presence of 
unpaired electrons. This gives rise to properties like high density, high 
enthalpies of atomization, and high melting and boiling points. 
b.  Atomic radii: The atomic radii decrease from Sc to Cr because the 
effective nuclear charge increases. The atomic size of Fe, Co, Ni is 
almost same because the attraction due to increase in nuclear charge 
is cancelled by the repulsion because of increase in shielding effect. Cu 
and Zn have bigger size because the shielding effect increases and 
electron electron repulsions repulsion increases.  
c. Lanthanoid Contraction: The steady decrease in the atomic and ionic 
radii of the transition metals as the atomic number increases. This is 
because of filling of 4f orbitals before the 5d orbitals. This contraction 
is size is quite regular. This is called lanthanoid contraction. It is 
because of lanthanoid contraction that the atomic radii of the second 
row of transition elements are almost similar to those of the third row 
of transition elements.  
d. Ionisation enthalpy: There is slight and irregular variation in ionization 
energies of transition metals due to irregular variation of atomic size. 
The I.E. of 5d transition series is higher than 3d and 4d transition 
series because of Lanthanoid Contraction. 
e. Oxidation state: Transition metals show variable oxidation states due 
to tendency of (n-1)d as well as ns electrons to take part in bond 
formation. 
f. Magnetic properties: Most of transition metals are paramagnetic in 
nature due to presence of unpaired electrons. It increase s from Sc to 
Cr and then decreases because number of unpaired and then decrease 
because number of unpaired electrons increases from Sc to Cr and 
then decreases. 
g. Catalytic properties: Most of transition metals are used as catalyst 
because of (i) presence of incomplete or empty d – orbitals, (ii) large 
surface area, (iii) varuable oxidation state, (iv) ability to form 
complexes, e.g., Fe, Ni, V
2
O
3
, Pt, Mo, Co and used as catalyst. 
h. Formation of coloured compounds: They form coloured ions due to 
presence of incompletely filled d – orbitals and unpaired electrons, 
they can undergo d – d transition by absorbing colour from visible 
region and radiating complementary colour. 
i. Formation of complexes: Transition metals form complexes due to (i) 
presence of vacant d – orbitals of suitable energy (ii) smaller size (iii) 
higher charge on cations. 
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j. Interstitial compounds: Transition metals have voids or interstitials in 
which C, H, N, B etc. can fit into resulting in formation of interstitial 
compounds. They are non – stoichiometric, i.e., their composition is 
not fixed, e.g., steel. They are harder and less malleable and ductile. 
k. Alloys formation: They form alloys due to similar ionic size. Metals can 
replace each other in crystal lattice, e.g., brass, bronze, steel etc. 
9. Preparation of Potassium dichromate (K
2
Cr
2
O
7
): 
 It is prepared by fusion of chromate ore (FeCr
2
O
4
) with sodium 
carbonate in excess of air. 
 4FeCr
2
O
4
 + 8Na
2
CO
3
 + 7O
2
  ? ?? ? 8Na
2
CrO
4
 + 2Fe
2
O
3
 + 8CO
2
  
 2Na
2
CrO
4
 + H
2
SO
4
 ? ?? ? Na
2
Cr
2
O
7
 + H
2
O + Na
2
SO
4
 Sodium    Sodium 
 chromate    dichromate 
 Na
2
Cr
2
O
7
 + 2KCl ? ?? ? K
2
Cr
2
O
7
 + 2NaCl 
10. Effect of pH on chromate and dichromate ions: The chromates and 
dichromates are interconvertible in aqueous solution depending upon 
pH of the solution. The oxidation state of chromium in chromate and 
dichromate is the same. 
2 CrO
4
2-
 + 2H
+
 ? Cr
2
O
7
2-
 + H
2
O 
Cr
2
O
7
2-
 + 2 OH- ? 2 CrO
4
2-
+ H
2
O 
11. Potassium dichromate acts as a strong oxidizing agent in acidic 
medium. 
                 Cr
2
O
7
2-
 +14 H
+
 + 6e
-
 ? 2 Cr
3+
 + 7 H
2
O  
 
12. Preparation of Potassium permanganate (KMnO
4
): 
a.  Potassium permanganate is prepared by fusion of MnO
4
 with alkali 
metal hydroxide (KOH) in presence of O
2
 or oxidising agent like KNO
3
.  
It produces dark green K
2
MnO
4
 which undergoes oxidation as well as 
reduction in neutral or acidic solution to give permanganate. 
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 4
  
22 24
2
442
2MnO 4KOH O 2K MnO 2H O
4H 3MnO 2MnO MnO 2H O
+- -
++ ????+
+????+ +
2
2
)
Or 
 Commercially it is prepared by the alkaline oxidative fusion of MnO
2
 
followed by the electrolytic oxidation of manganate (Vl). 
  
()
fused with KOH 2
24
in the presence of O or KNO
23
manganate ions
MnO MnO
-
? ? ?? ??? ?? ??? ? ?
  
() (
electrolytic oxidation in alkaline medium 2
44
Green P urple
MnO MnO
--
? ? ?? ?? ?? ?? ?? ? ?? ??
(ii) In laboratory, Mn²
+
 salt can be oxidized by peroxodisulphate ion to 
permanganate ion. 
 
2+ 2- 2
28 2 4 4
2Mn + 5S O +8H O 2MnO 10SO 16H
- -+
?? ??+ + 
13. Potassium permanganate acts as a strong oxidizing agent in acidic, 
neutral or faintly basic medium. 
 In acidic medium. 
 MnO
4
-
 + 8 H
+
 + 5 e
-
 ? Mn
2+
 + 4 H
2
O 
 In neutral or faintly basic medium, 
 MnO
4
-
 + 3 e
-
 + 2 H
2
O ? MnO
2
 + 4OH
-
14. Properties of Lanthanoids and Actinoids.  
 Lanthanoids Actinoids  
+3 oxidation state is most common 
along with +2 and +4 
Actiniods also show higher oxidation 
states such as +4, +5, +6 and +7. 
 
They are more reactive  
Except Promethium, they are non – 
radioactive. 
They are radioactive 
The magnetic properties of 
lanthanoids are less complex than 
actinoids. 
The magnetic properties of the 
actinoids are more complex than 
those of the lanthanoids 
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15. Mischmetall - It is a well known alloy which consists of a lanthanoid 
metal (~ 95%) and iron (~ 5%) and traces of S, C, Ca and Al. A good 
deal of mischmetall is used in Mg-based alloy to produce bullets, shell 
and lighter flint. 
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