d- Block Elements
Transcript d- Block Elements
By : A P Singh
Definition of d-block elements
The elements of periodic table belonging
to group 3 to 12 are known as d-Block
elements. because in these elements last
electron enters in d sub shell or d orbital .
The d -block elements lies in between s- and
p-block elements in the long form of
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. i.e.
A transition element should have
partially filled (n-1) d orbital.
Group 7 Presentation
How are d - Block Elements &
Transition elements different?
All d block elements are not transition
elements but all transition elements are dblock elements
All d block elements are not transition
elements because d block elements like
Zinc have full d10 configuration in their
ground state as well as in their common
oxidation state.which is not according to
definition of transition elements.
1. Which of the d-block elements may not be
regarded as the transition elements?
2. Why Zn, Cd and Hg are not considered as
3. Why Scandium is a transition element but Zinc
4. Copper atom has completely filled d orbital
(3d10) in its ground state, yet it is transition
5. Silver atom has completely filled d orbital
(4d10) in its ground state, yet it is transition
6. Why the very name ‘transition’ given to the
elements of d-block .
Zn, Cd and Hg
Because they do not have vacant d-orbitals neither in the
atomic state nor in any stable oxidation state.
Scandium is a transition because it has incompletely filled d
orbitals in its ground state but Zinc have full d10
configuration in their ground state as well as in their common
Copper (Z = 29) can exhibit +2 oxidation state wherein it will
have incompletely filled d-orbitals (3d), hence a transition
Silver (Z = 47) can exhibit +2 oxidation state wherein it will
have incompletely filled d-orbitals (4d), hence a transition
The very name ‘transition’ given to the elements of d-block is
only because of their position between s– and p– block
GENERAL & PHYSICAL PROPERTIES OF D-BLOCK ELEMENTS
ATOMIC & IONIC SIZE
OXIDATION STATES OF D-BLOCK ELEMENTS
FORMATION OF COMPLEX COMPOUNDS
FORMATION OF INTERSTITIAL COMPOUNDS
MELTING AND BOILING POINTS (ENTHALPIES OF ATOMISATION) :
melting and boiling
points are high.
A large number of
take part in bonding
so they have very
strong metallic bonds
and hence high m.pt
They have high
atomisation . The
maxima is at about
the middle of each
A large number of
bonding so they
have very strong
metallic bonds and
ATOMIC & IONIC SIZE
Along the rows nuclear charge increases but
the penultimate d-sub shell has poor shielding
effect so atomic and ionic size remain almost
The radii of the third (5d) series are
virtually the same as those of the
corresponding members of the second
phenomenon is associated with the
intervention of the 4f orbital, the filling of
4f before 5d orbital results in a regular
decrease in atomic radii called Lanthanoid
contraction which essentially compensates
for the expected increase in atomic size with
increasing atomic number.
net resultof the lanthanoid contraction is
that the second and the third d series exhibit
similar radii (e.g., Zr 160 pm, Hf 159 pm)
IE2 :V < Cr > Mn and Ni < Cu > Zn
IE3 : Fe << Mn
to an increase in nuclear charge which
the filling of the inner
dorbitals , There is an increase in ionization
enthalpy along each series of the transition
elements from left to right.
many small variations occur.
• Transition elements have variable oxidation
states ,due to very small energy difference
between (n-1)d & ns sub-shell electrons from
both the sub-shell take part in bonding
• The elements which give the greatest number of
oxidation states occur in or near the middle of the
series. Manganese, for example, exhibits all the
oxidation states from +2 to +7.
oxidation states are found when a complex
compound has ligands capable of π-acceptor character
in addition to the σ-bonding.
example, in Ni(CO)4 and Fe(CO)5, the oxidation
state of nickel and iron is zero.
Trends in the M2+/M Standard Electrode Potentials
Most of the transition metal compounds (ionic
as well as covalent) are coloured both in solid
state & in aqueous state.
Generally the elements/ions having unpaired
electrons produce coloured compound.
Splitting of d-orbital energies by an octahedral field of ligands
complex in electronic
Ground State (GS)
An artist’s wheel
Q1.Of the ions Ag+, Co2+ & Ti4+ which one will be
coloured in aqueous soln. ?
Q2. Why hydrated copper sulphate is blue while
anhydrous copper sulphate is white?
Q3.[Ti(H2O)6]3+ is coloured while [Sc(H2O)6]3+ is
colourless . Explain?
Q4. Why transtion metals & their compounds act as
Q5. Why transtion metals generally forms coloured
Vanadium(V) oxide,V2O5 (in Contact Process)
Finely divided iron (in Haber’s Process)
Nickel (in Catalytic Hydrogenation)
Cobalt (Synthesis of gasoline)
This property is due to Presence of unpaired electrons in their
incomplete d orbitals.
Variable oxidation state of transition metals.
In most cases , provide large surface area with
iron(III) catalyses the reaction between iodide
and per sulphate ions
When a magnetic field is applied to substances,
mainly two types of magnetic behaviour are
observed: diamagnetism and paramagnetism.
Diamagnetic substances are repelled by the applied
field while the paramagnetic substances are
Substances which are attracted very strongly are said
to be ferromagnetic.
In fact, ferromagnetism is an extreme form of
Most of the transition elements and their compounds
Paramagnetism arises from the presence of unpaired
electrons, each such electron have a magnetic
The magnetic moment of any transition element or its
compound/ion is given by (assuming no contribution
from the orbital magnetic moment).
μs = √n(n+2) BM
Here n is the number of unpaired electrons
The paramagnetism first increases in any transition
element series, and then decreases. The maximum
paramagnetism is seen around the middle of the series.
QUESTIONSQ. 1: Which ion has maximum magnetic moment
Q.2. What is the magnetic moment of Mn2+
25) in aqueous solution ?
Ans.- With atomic number 25, the divalent Mn2+ ion in
aqueous solution will have d5 configuration (five
unpaired electrons).Hence, The magnetic moment, μ
μ = √5(5 + 2) = 5.92BM
Complex compounds are those in which the metal
ions bind a number of anions or neutral molecules
giving complex species with characteristic
The transition metals form a large number of
A few examples are: [Fe(CN)6]3–, [Fe(CN)6]4–,
[Cu(NH3)4]2+ and [PtCl4]2–.
This property is due to the
comparatively smaller sizes of the metal ions
their high ionic charges and the
availability of d orbitals for bond formation.
FORMATION OF INTERSTITIAL COMPOUNDS
transition elements form a large number
of interstitial compounds in which small atoms
such as hydrogen, carbon, boron and nitrogen
occupy the empty spaces in their lattices.
are usually non stoichiometric and are
neither typically ionic nor covalent,
example, TiC, Mn4N, Fe3H, VH0.56 and
characteristics of these compounds are -:
a) high melting points, higher than
b) very hard.
c) retain metallic conductivity.
d) chemically inert.
Oxides and Oxoanions of Metals
All the metals except scandium form MxOy oxides which
As the oxidation number of a metal increases, ionic
In higher oxides, the acidic character is predominant
Potassium dichromate K2Cr2O7
Dichromates are generally prepared from chromate, which in
turn are obtained by the fusion of chromite ore (FeCr2O4)
with sodium or potassium carbonate in free access of air.
4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2
2Na2CrO4 + 2 H+
→ Na2Cr2O7 + 2 Na+ + H2O
Na2Cr2O7 + 2 KCl → K2Cr2O7 + 2 NaCl
The chromate ion is tetrahedral whereas the dichromate
ion consists of two tetrahedra sharing one corner with
Cr–O–Cr bond angle of 126°.
In acidic solution,its oxidising action can be represented as
Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O ;
a) 6 I– → 3I2 + 6 e–
c) 3 Sn2+ → 3Sn4+ + 6 e–
b) 3 H2S → 6H+ + 3S + 6e–
d) 6 Fe2+ → 6Fe3+ + 6 e–
Potassium Permanganate, KMnO4
prepared by fusion of MnO2 with an alkali metal hydroxide
and an oxidising agent(O2 or KNO3) this produces the dark
green K2MnO4 which disproportionates in a neutral or acidic
solution to give permanganate.
2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
3MnO42– + 4H+ → 2MnO4– + MnO2 + 2H2O
In the laboratory, a manganese (II) ion salt is oxidised by
peroxodisulphate to permanganate.
2Mn2+ + 5S2O82– + 8H2O → 2MnO4– + 10SO42– + 16H+
Oxidising Properties : Strong oxidising agent in acidic as well as in neutral
& basic medium :
Questions for Practice
1. Complete the following reactions :
a) MnO4- (aq.) + C2O42-(aq) + H+(aq) ------->
b) Cr2O7-- + H2S + H+ ----->
Fe3+ + I- -------->
CrO4 2- + H+ ------>
MnO4- (aq.)+S2O3--(aq.) + H2O(l)
Cr2O7-- (aq.)+ Fe2+ (aq.)+ H+ (aq.)
Cu++ (aq) + I- (aq) -------->
Cr2O7-- (aq.)+ I- (aq.)+ H+ (aq.) ----->
MnO4- (aq.) + NO2-(aq) + H+(aq) ---->
2. What is meant by lanthanoid contraction ?
3. Describe the preparation of following compounds –
i. Potassium dichromate from Sodium chromate.
ii. KMnO4 from K2MnO4
A. Explain the following :1. Cu(l) is not stable in an aq. solution.
2. With same (d4) configuration Cr(ll) is reducing whereas Mn (lll) is
3. Transition metals are in general act as good catalyst.
4. Metal- metal bonding is more extensive in 4d & 5d series of
transition metals than the 3d series.
5. Mn(lll) undergoes disproportionation reaction easily.
6. Co(ll) is easily oxidised in presence of strong ligands.
7. In a transition series of metals , the metals which exhibits the
greatest No. of oxdn. occurs in the middle of the series .
8. Unlike Cr3+, Mn2+, Fe3+ & subsequent other M2+ ions of the 3d series
of the elements , the 4d and 5d series metals generally do not form
stable cationic species.
9. Transition metals and their compounds generally exhibits
10. Actinoids exhibits greater range of oxdn states than lanthenoids.
11. Transition metals generally forms coloured compounds .
12. Mn exhibits the highest oxdn state of +7 among the 3d series of
13. The enthalpy of atomisation of transition metals ar quite high.
14. There is a close similarity in physical & chemical properties of the
4d & 5d series of the transition metals , much more than the
expected on the basis of usual family relationship.
15. The oxidising power of oxoanions are in the order –
VO2+ < Cr2O7-- < MnO416. The third ionisation enthalpy of Mn is exceptionally high.
17. Cr 2+ is a stonger reducing agent than Fe 2+
18. La 3+ (Z= 57) and Lu3+(Z= 71) do not show any colour in solution
19. Among the divalent cations of the first transition series elements,
20. Mn exhibits the maximum paramagnetism .
21. Generally there is an increase in density of elements from Ti
(Z= 22) to Cu (Z= 29). in the 3d series of metals.
22. The atomic radii of the metals of third (5d) series of transition
metals are virtually the same as those of the corresponding
members of the second(4d) series.
23. The Eo value for Mn3+/ Mn2+ couple is much more positive than that
for Cr3+/Cr2+ couple or Fe3+/Fe2+ couple.
24. The highest oxdn state of a metal is exhibited in its oxides or
25. Zn is not regarded as a transition metal.
26. Explain why Ce4+ is a strong oxidising agent.
27. Many of the transition elements form interstitial compound
28. Lanthanoid form primarily +3 ions , while the actinoids have higher
oxdn statesin their compounds, +4 or even +6 being typical.
29. Co2+ is easily oxidised to Co3+ in the presence of a strong ligand.
30. CO is stronger complexing ligand than NH3 .
31. Mn2+ is much more resistant than Fe2+ towards oxdn.
32. The enthalpies of atomisation of transition metals are quite high.
33.There occur much more frequent metal-metal bonding in
compounds of 3rd (5d) transition series of d-block elements.
34. The Eo value for Cu2+/ Cu couple is positive in the 1st series
(rest have negative).
35. With the same d-orbital configuration (d4) Cr 2+ is a reducing agent
while M4+ is an oxidising agent.