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CHAPTER

8

The d- and
f- Block Elements

8
...
2 Electronic Configurations of the d-Block
Elements
8
...
4 Some Important Compounds of Transition
Elements
8
...
6 The Actinoids
8
...
1

8
...
3

8
...

8 Maximum VSA type questions were asked from
General Properties of the Transition Elements
(d-Block)
...
5

8
...
7

8 Maximum SA and LA I type questions
were asked from General Properties of the
Transition Elements (d-Block)
...

8 Their general electronic configuration is
(n – 1)d1 – 10ns0 – 2
...

Form coloured compounds due to d-d transitions
Transition metal ions and their compounds are paramagnetic due to presence
of unpaired electrons in the (n – 1)d-orbitals and it is calculated by using the
formula, m =

Catalytic behaviour
Interstitial compounds
Alloy formation

n(n + 2) where, n is the no
...


Due to variable oxidation states and ability to form complexes
Due to empty spaces in their lattices, small atoms can be easily accommodated
Due to similar atomic sizes

8 Some important compounds :
Compounds
Potassium dichromate
(K2Cr2O7)

O 179 pm O
O Cr 126°
O

2–

O
Cr
O
16
3p O
m

Potassium permanganate
(KMnO4)

O

O

Mn
O

O–

Preparation

Properties

Uses

From sodium dichromate
(obtained from chromite
ore)
4FeCr2O4 + 8Na2CO3 + 7O2
8Na2CrO4 + 2Fe2O3
+ 8CO2
2Na2CrO4 + 2H+
Na2Cr2O7 + 2Na+ + H2O
Na2Cr2O7 + 2KCl
K2Cr2O7 + 2NaCl

Orange red crystalline solid,
oxidising agent having melting
point 398°C
...


From potassium
manganate (obtained from
pyrolusite)
2MnO2 + 4KOH + O2
2K2MnO4 + 2H2O
2K2MnO4 + Cl2
2KMnO4 + 2KCl

Deep purple crystalline solid,
oxidising agent, having melting
point 240°C
...


X

Volumetric titrations involving KMnO4 are carried out only in the presence of dil
...
H2SO4 does not give any oxygen of its own to oxidise the
reducing agent
...
Cerium (at
...
58) to lutetium (at
...
71)
...
Thorium (at
...
90) to lawrencium (at
...
103)
...


Oxidation states

Most common oxidation state of lanthanoids is +3
...
g
...


Action of air

All the lanthanoids are silvery white soft metals and tarnish readily in
moist air
...


Coloured ions

They form coloured trivalent metal ions due to f-f transitions of unpaired
electrons
...


Magnetic properties

La3+, Lu3+ are diamagnetic while trivalent ions of the rest of lanthanoids
are paramagnetic
...


Electropositive character Highly electropositive because of low ionisation energies
...


Tendency to form
complexes

Lanthanoids do not have much tendency to form complexes due to low
charge density because of their large size
...


8 Lanthanoid contraction : In lanthanoid
series, with increasing atomic number, there
is progressive decrease in atomic/ionic radii
(M3+ ions) from La3+ to Lu3+
...


X

Consequences : Their separation is difficult,
they have small differences in properties
and 4d and 5d transition series have almost
same atomic radii (Zr and Hf have similar
properties due to same size)
...
It is used to make tracer bullets,
shells and lighter flints
...
Actinoid contraction
is greater due to poor sheilding effect of the 5f-electrons
...


Oxidation states

Like lanthanoids, most common oxidation state is +3
...
g
...

They show a large number of oxidation states because of very small energy
gap between 5f, 6d and 7s subshells
...

Coloured ions

Coloured due to f-f transition except Ac3+(5f 0), Cm3+(5f 7) and Th4+(5f 0)
which are colourless
...


Density

All actinoids except thorium and americium have high densities
...

Ionisation energy

They have low ionisation energies than lanthanoides
...


Electropositive
character

Highly electropositive metals
...
U and Pu are used as fuel
in nuclear reactor
...

and +7 besides +3
...


All actinoids are radioactive
...


They form oxo-cations like UO2, PuO2, UO 2, etc
...


Actinoid compounds are more basic
...


They have greater tendency of complex
formation
...
2 Electronic Configurations of
the d-Block Elements
VSA

(1 mark)

1
...

(1/5, 2020)
2
...

(1/5, AI 2014)
(2
marks)
SA
3
...

(Delhi 2015)

8
...
In general, the electronic
configuration of these elements is (n – 1)d1 – 10
ns1 – 2
...
e
...
However, Zn, Cd and Hg are
not regarded as transition elements
...
Transition metals are hard (except
Zn, Cd and Hg) and have a high melting point
...
Why are Zn, Cd and Hg non-transition
elements?
5
...
Why do transition metals and their
compounds show catalytic activity?

7
...


Why is Cu2+ ion coloured while Zn2+ ion is
colourless in aqueous solution?

9
...
Out of the following transition elements, the
maximum number of oxidation states are
shown by
(a) Sc (Z = 21)
(b) Cr (Z = 24)
(c) Mn (Z = 25) (d) Fe (Z = 26)
...
Assertion (A) : Transition metals have high
melting point
...

(a) Both Assertion (A) and Reason (R) are
correct statements, and Reason (R) is
the correct explanation of the Assertion
(A)
...

(c) Assertion (A) is correct, but Reason (R)
is incorrect statement
...

(2020)
12
...


(1/5, 2020)
13
...

(Delhi 2017)
14
...


(Delhi 2017)
15
...
Zn2+ salts are white while Cu2+ salts are
coloured
...
Why do transition elements show variable
oxidation states?
(Delhi 2014C)
18
...

(1/2, Delhi 2011)
19
...


(1/2, AI 2011)

SA

(2 marks)

20
...
 (2/5, 2020)
21
...
Give reasons for the following :

(i) Transition metals form alloys
...


(2/3, Delhi 2019)
23
...
91 –1
...
44

–0
...
41 +1
...
77

+1
...
(i) How is the variability in oxidation states
of transition metals different from that
of the p-block elements?
(ii) Out of Cu+ and Cu2+, which ion is
unstable in aqueous solution and why?

(2/5, Delhi 2017)
25
...


(ii) Zn, Cd and Hg are soft metals
...
Give reasons :
(i) Mn shows the highest oxidation state
of +7 with oxygen but with fluorine it
shows the highest oxidation state of +4
...

(2/3, Delhi 2016)
27
...

(ii) Cu+ ion is unstable in aqueous solution
...
Why do transition elements show variable
oxidation states? In 3d series (Sc to Zn),
which element shows the maximum number
of oxidation states and why? (Foreign 2015)
29
...

(ii) Transition metals and their compounds
show catalytic properties
...
What is meant by ‘disproportionation’? Give
an example of a disproportionation reaction
in aqueous solution
...
Account for the following :
(i) Mn2+ is more stable than Fe2+ towards
oxidation to +3 state
...

(Delhi 2014)
32
...

(ii)
Which of the 3d-block elements may
not be regarded as the transition
elements and why? (2/3, Foreign 2014)
33
...


(ii) The ionisation enthalpies (first and
second) in the first series of the
transition elements are found to vary
irregularly
...
Assign reasons for the following :
(i) Copper(I) ion is not known to exist in
aqueous solutions
...

(AI 2014C)
35
...

(ii) Cobalt (II) is very stable in aqueous
solutions but gets easily oxidised in the
presence of strong ligands
...
Assign reasons for the following :
(i) Cu(I) ion is not known to exist in
aqueous solutions
...

(2/3, AI 2014C)
37
...

(ii) Transition metals generally form
coloured compounds
...
(i) 
Which metal in the first transition
series (3d-series) exhibits +1 oxidation
state most frequently and why?

(ii) Which of following cations are coloured
in aqueous solutions and why?
Sc3+, V3+, Ti4+, Mn2+

(At
...
Sc = 21, V = 23, Ti = 22, Mn = 25)
(Delhi 2013)
39
...

(ii) Transition metals and their compounds
act as catalyst
...
How would you account for the following?
(i) Many of the transition elements are
known to form interstitial compounds
...


(2/3, Delhi 2012)
41
...


43
...


45
...


47
...


(d4) Cr2+ is a reducing agent while Mn3+
is an oxidising agent
...

(2/3, Delhi 2012)
How would you account for the following :
(i) The E°M2+/M for copper is positive
(+0
...
Copper is the only metal in
the first series of transition elements
showing this behaviour
...
(2/3, AI 2012)
Explain the following observations :
(i) Many of the transition elements are
known to form interstitial compounds
...

(2/3, AI 2012)
Explain the following observations
...

(ii) There is hardly any increase in atomic
size with increasing atomic numbers in
a series of transition metals
...

(ii) The transition metals and many of their
compounds act as good catalysts
...

(ii) The Fe2+ is much more easily oxidised to
Fe3+ than Mn2+ to Mn3+
...

(2/5, AI 2012C)
Account for the following :
(i) Mn2+ compounds are more stable than
Fe2+ compounds towards oxidation to
their +3 state
...


(2/5, AI 2012C)
49
...

(ii)
Manganese exhibits the highest
oxidation state of +7 among the 3rd
series of transition elements
...
How would you account for the following :
(i) Cr2+ is reducing in nature while with
the same d-orbital configuration (d4)
Mn3+ is an oxidising agent
...

(AI 2011)
51
...

(ii) Unlike Cr3+, Mn2+, Fe3+ and the
subsequent other V2+ ions of the 3d
series of elements, the 4d and the 5d
series metals generally do not form
stable cationic species
...
Explain giving a suitable reason for each of
the following :
(i) Transition metals and their compounds
are generally found to be good catalysts
...


(AI 2011)

LA I

(3 marks)

53
...

(ii) unstable in aqueous solution
...

Give suitable reason in each
...
Give reasons :
(i) Eº value for Mn3+/Mn2+ couple is much
more positive than that for Fe3+/Fe2+
...


(iii) Sc3+ is colourless in aqueous solution
whereas Ti3+ is coloured
...
Account the following :
(i) Transition metals form large number of
complex compounds
...

(iii) E° value for the Mn3+/Mn2+ couple is
highly positive (+1
...

(3/5, Delhi 2017)
56
...
Account for the following :
(i) Mn shows the highest oxidation state
of +7 with oxygen but with fluorine, it
shows the highest oxidation state of +4
...

(iii) Cu2+ salts are coloured, while Zn2+ salts
are white
...
E°(M2+/M)

Cr Mn
Fe
Co
Ni
Cu
–0
...
18 –0
...
28 –0
...
34

From the given data of E° values, answer the
following questions :
(i) Why is E°(Cu2+/Cu) value exceptionally
positive?
(ii) Why is E°(Mn2+/Mn) value highly negative
as compared to other elements?
(iii) Which is a stronger reducing agent Cr2+
or Fe2+? Give reason
...
Assign suitable reasons for the following :
(i) The Mn2+ compounds are more stable
than Fe2+ towards oxidation to their +3
state
...



60
...


62
...


64
...

(Foreign 2014)
Give reasons for the following :
(i) Mn3+ is a good oxidising agent
...

(iii) Although ‘F’ is more electronegative
than ‘O’, the highest Mn fluoride is
MnF4, whereas the highest oxide is
Mn2O7
...

(ii) The enthalpies of atomization of the
transition metals are high
...


(3/5, AI 2013C)
Explain the following :
(i) Copper (I) ion is not stable in an
aqueous solution
...

(iii) Transition metals in general act as good
catalysts
...

(ii) Mn (III) undergoes disproportionation
reaction easily
...
 (3/5, Foreign 2011)
Account for the following :
(i) The transition metals and their
compounds act as good catalysts
...

(iii) A transition metal exhibits higher
oxidation states in oxides and fluorides
...
The elements of 3d transition series are given
as
Sc Ti V Cr Mn Fe Co Ni Cu Zn

Answer the following :
(i) Write the element which shows
maximum number of oxidation states
...

(ii) Which element has the highest melting
point?
(iii) Which element shows only +3 oxidation
state?
(iv) Which element is a strong oxidising
agent in +3 oxidation state and why?

(AI 2016)

8
...
Account for the following :

Chromates change their colour when kept
in an acidic solution
...
Orange colour of Cr2O72– ion changes to
yellow when treated with an alkali
...
Complete the following equation :
2MnO4– + 6H+ + 5NO2–


(1/2, Delhi 2015)
69
...
Complete the following equation :
MnO4– + 8H+ + 5e–

(1/5, Delhi 2014)
71
...
Give reason :
Orange solution of potassium dichromate
turns yellow on adding sodium hydroxide to
it
...
Write the balanced chemical equations
involved in the preparation of KMnO4 from
pyrolusite ore (MnO2)
...
Write the balanced ionic equations showing
the oxidising action of acidified dichromate
(Cr2O2–
7 ) solutions with (i) iron (II) ion and
(ii) tin (II) ion
...
When MnO2 is fused with KOH in the
presence of KNO3 as an oxidizing agent,

it gives a dark green compound (A)

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