d-block-elements.pptx.pdf

Chemistry project

1. *The d- Block
Elements

3. 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 periodic
table

Definition of d-block elements

5. 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.


Transition Elements

6. Group 7 Presentation

8. All d block elements are not transition
elements but all transition elements are
d-block elements

All d block elements are not transition
elements because d block elements like Zinc
have full d
10
configuration in their ground
state as well as in their common oxidation
state.which is not according to definition of
transition elements.
How are d - Block Elements &
Transition elements different?

9. 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
transition elements.
3.Why Scandium is a transition element but Zinc
is not.
4.Copper atom has completely filled d orbital
(3d
10
) in its ground state, yet it is transition
element. Why
5.Silver atom has completely filled d orbital
(4d
10
) in its ground state, yet it is transition
element. Why
6.Why the very name ‘transition’ given to the
elements of d-block .

10. 1.Zn, Cd and Hg

2.Because they do not have vacant d-orbitals neither in the
atomic state nor in any stable oxidation state.

3.Scandium is a transition because it has incompletely filled d
orbitals in its ground state but Zinc have full d
10

configuration in their ground state as well as in their common
oxidation state

4.Copper (Z = 29) can exhibit +2 oxidation state wherein it will
have incompletely filled d-orbitals (3d), hence a transition
element.

5.Silver (Z = 47) can exhibit +2 oxidation state wherein it will
have incompletely filled d-orbitals (4d), hence a transition
element.

6.The very name ‘transition’ given to the elements of d-block is
only because of their position between s– and p– block
elements.





Answers

11. GENERAL & PHYSICAL PROPERTIES OF D-BLOCK ELEMENTS
PHYSICAL PROPERTIES
ATOMIC & IONIC SIZE
IONIZATION ENTHALPY
OXIDATION STATES OF D-BLOCK ELEMENTS
COLOURED IONS
CATALYTIC PROPERTIES
MAGNETIC PROPERTIES
FORMATION OF COMPLEX COMPOUNDS
FORMATION OF INTERSTITIAL COMPOUNDS

12. PHYSICAL PROPERTIES

13. MELTING AND BOILING POINTS (ENTHALPIES OF ATOMISATION)
:
melting and boiling
points are high.
A large number of
unpaired electrons
take part in bonding
so they have very
strong metallic bonds
and hence high m.pt
& b.pt

14. They have high
enthalpies of
atomisation . The
maxima is at about
the middle of each
series.
A large number of
unpaired electrons
take part in
bonding so they
have very strong
metallic bonds and
hence high
enthalpy of
atomization.

15. ATOMIC & IONIC SIZE

17. Along the rows nuclear charge increases but
the penultimate d-sub shell has poor shielding
effect so atomic and ionic size remain almost
same .
The radii of the third (5d) series are
virtually the same as those of the
corresponding members of the second
series.

18. This 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.

The 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)

19. IONIZATION ENTHALPIES
IE
2
:V < Cr > Mn and Ni < Cu > Zn

IE
3
: Fe << Mn

20. Due to an increase in nuclear charge which
accompanies the filling of the inner d-
orbitals , There is an increase in ionization
enthalpy along each series of the transition
elements from left to right.

However, many small variations occur.

21. •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
oxidation states

22. •Low oxidation states are found when a complex
compound has ligands capable of π-acceptor character
in addition to the σ-bonding.
*For example, in Ni(CO)4 and Fe(CO)5, the oxidation
state of nickel and iron is zero.
•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.

23. Trends in the M
2+/
M Standard Electrode Potentials

24. 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.

COLOURED IONS

25. Scandium
oxide
Vanadyl
Sulphate
dihydrate
Titanium
oxide
sodium
chromatePotassium
ferricyanide
Nickel(II)
nitrate
hexa-
hydrate
Zinc
sulfate
Hepta-
hydrate
Mangnaese(II)
chloride
tetrahydrate
Cobalt(II)
chloride
Copper(II)
sulfate
penta-
hydrate

27. Splitting of d-orbital energies by an octahedral field of ligands

28. ES
GS
e
g
t
2g
hv
e
g
t
2g
Δ
o


ES
GS
complex in electronic
Ground State (GS)

d-d
transition

complex in
electronic
excited state
(ES)

29. An artist’s wheel

31. Questions:

Q1.Of the ions Ag
+
, Co
2+
& Ti
4+
which one will be
coloured in aqueous soln. ?

Q2. Why hydrated copper sulphate is blue while
anhydrous copper sulphate is white?

Q3.[Ti(H
2
O)
6
]
3+
is coloured while [Sc(H
2
O)
6
]
3+
is
colourless . Explain?
Q4. Why transtion metals & their compounds act as
good catalyst?

Q5. Why transtion metals generally forms coloured
compounds

32. CATALYTIC
PROPERTIES
✔Vanadium(V) oxide,V
2
O
5
(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
free valencies.

33. iron(III) catalyses the reaction between iodide
and per sulphate ions
For example
Explanation

34. MAGNETIC PROPERTIES
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
attracted.
Substances which are attracted very strongly are said
to be ferromagnetic.

In fact, ferromagnetism is an extreme form of
paramagnetism.

35. Most of the transition elements and their compounds
show paramagnetism.
Paramagnetism arises from the presence of unpaired
electrons, each such electron have a magnetic
moment.
The magnetic moment of any transition element or its
compound/ion is given by (assuming no contribution
from the orbital magnetic moment).

μ
s
  = √n(n+2) BM

Here n is the number of unpaired electrons

37. The paramagnetism first increases in any transition
element series, and then decreases. The maximum
paramagnetism is seen around the middle of the series.

38. QUESTIONS-
Q. 1: Which ion has maximum magnetic moment
  (a) V
3+
                                   (b) Mn
3+

  (c) Fe
3+
                                 (d) Cu
2+
 
Ans: c
Q.2. What is the magnetic moment of Mn
2+
ion (Z=
25) in aqueous solution ?
Ans.- With atomic number 25, the divalent Mn
2+
ion in
aqueous solution will have d
5
configuration (five
unpaired electrons).Hence, The magnetic moment, μ
is
μ = √5(5 + 2) = 5.92BM

39. FORMATION OF COMPLEX COMPOUNDS
Complex compounds are those in which the metal
ions bind a number of anions or neutral molecules
giving complex species with characteristic
properties.

The transition metals form a large number of
complex compounds.

A few examples are: [Fe(CN)6]
3–
, [Fe(CN)6]
4–
,
[Cu(NH3)4]
2+
and [PtCl4]
2–
.

40. 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.

41. The 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.

They are usually non stoichiometric and are
neither typically ionic nor covalent,

for example, TiC, Mn4N, Fe3H, VH0.56 and
TiH1.7, etc.

FORMATION OF INTERSTITIAL COMPOUNDS

42. Fe
C

43. The principal physical and chemical
characteristics of these compounds are -:

a)high melting points, higher than those of
pure metals.
b)very hard.

c)retain metallic conductivity.

d)chemically inert.

44. Oxides and Oxoanions of Metals
All the metals except scandium form M
x
O
y
oxides which
are ionic.
As the oxidation number of a metal increases, ionic
character decreases.
In higher oxides, the acidic character is predominant
V
2
O
2
< V
2
O
4
< V
2
O
5
.
Less basic more basic amphoteric

45. Potassium dichromate K
2
Cr
2
O
7
Preparation :
Dichromates are generally prepared from chromate, which in
turn are obtained by the fusion of chromite ore (FeCr
2
O
4
)
with sodium or potassium carbonate in free access of air.
4 FeCr
2
O
4
+ 8 Na
2
CO
3
+ 7 O
2
→ 8 Na
2
CrO
4
+ 2 Fe
2
O
3
+ 8 CO
2

2Na
2
CrO
4
+ 2 H
+
→ Na
2
Cr
2
O
7
+ 2 Na
+
+ H
2
O
Na
2
Cr
2
O
7
+ 2 KCl → K
2
Cr
2
O
7
+ 2 NaCl

46. Structure :
The chromate ion is tetrahedral whereas the dichromate
ion consists of two tetrahedra sharing one corner with
Cr–O–Cr bond angle of 126°.

47. Properties
Oxidising Properties
In acidic solution,its oxidising action can be represented as
follows:
Cr
2
O
7
2–
+ 14H
+
+ 6e– → 2Cr
3+
+ 7H
2
O ;
e.g.
a) 6 I
–
→ 3I
2
+ 6 e– c) 3 Sn
2+
→ 3Sn
4+
+ 6 e
–


b) 3 H
2
S → 6H
+
+ 3S + 6e– d) 6 Fe
2+
→ 6Fe
3+
+ 6 e–

48. Potassium Permanganate, KMnO
4
Preparation :
prepared by fusion of MnO
2
with an alkali metal hydroxide
and an oxidising agent(O
2 or
KNO
3
) this produces the dark
green K
2
MnO
4
which disproportionates in a neutral or acidic
solution to give permanganate.
2MnO
2
+ 4KOH + O
2
→ 2K
2
MnO
4
+ 2H
2
O
3MnO
4
2–
+ 4H
+
→ 2MnO
4
–
+ MnO
2
+ 2H
2
O
In the laboratory, a manganese (II) ion salt is oxidised by
peroxodisulphate to permanganate.

2Mn
2+
+ 5S
2
O
8
2–
+ 8H
2
O → 2MnO
4
–
+ 10SO
4
2–
+ 16H
+

49. Properties
Oxidising Properties : Strong oxidising agent in acidic as well as in neutral
& basic medium :

51. Structure :

52. 1. Complete the following reactions :
a)MnO
4
-
(aq.) + C
2
O
4
2-
(aq) + H
+
(aq) ------->
b)Cr
2
O
7
--
+ H
2
S + H
+
----->
c)Fe
3+
+ I
-
-------->
d)CrO
4

2-
+ H
+
------>
e) MnO
4
-
(aq.)+S
2
O
3
--
(aq.) + H
2
O(l) ??????
f)Cr
2
O
7
--
(aq.)+ Fe
2+
(aq.)+ H
+
(aq.) ??????

g) KMnO
4
---->
h) Cu
++
(aq) + I
-
(aq)
-------->

i) Cr
2
O
7
--
(aq.)+ I
-
(aq.)+ H
+
(aq.) ----->
j) MnO
4
-
(aq.) + NO
2
-
(aq) + H
+
(aq) ---->

2. What is meant by lanthanoid contraction ?
3. Describe the preparation of following compounds –
i. Potassium dichromate from Sodium chromate.
ii. KMnO
4
from K
2
MnO
4


Questions for Practice

53. A. Explain the following :-
1.Cu(l) is not stable in an aq. solution.
2.With same (d
4
) configuration Cr(ll) is reducing whereas Mn (lll) is
oxidising.
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 Cr
3+
, Mn
2+
, Fe
3+
& subsequent other M
2+
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
paramagnetic behaviour.

54. 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
transition elements.
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 –
VO
2
+
< Cr
2
O
7
--
< MnO
4
-

16. 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 Lu
3+
(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.

55. 23. The E
o
value for Mn
3+
/ Mn
2+
couple is much more positive than that
for Cr
3+
/Cr
2+
couple or Fe
3+
/Fe
2+
couple.
24. The highest oxdn state of a metal is exhibited in its oxides or
fluorides.
25. Zn is not regarded as a transition metal.
26. Explain why Ce
4+
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. Co
2+
is easily oxidised to Co
3+
in the presence of a strong ligand.
30. CO is stronger complexing ligand than NH
3
.
31. Mn
2+
is much more resistant than Fe
2+
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 3
rd
(5d) transition series of d-block elements.
34. The E
o
value for Cu
2+
/ Cu couple is positive in the 1
st
series
(rest have negative).
35. With the same d-orbital configuration (d
4
) Cr
2+
is a reducing agent
while M
4+
is an oxidising agent.

56. THANKS