B.Sc II Chemistry of Transitional elements (i)

Chemistry : Undergraduate level

1. 23-1
Mr.G.M.Dongare
(M.Sc,B.Ed,SET)
Associate Professor
Dept.of Chemistry
Shri Shivaji Colege of Arts,Commerce and
Science College, Akola.
TRANSITION ELEMENTS AND THEIR
COORDINATION COMPOUNDS
Academic year 2018-19

2. 23-2
The Transition Elements and Their Coordination
Compounds
23.1 Properties of the Transition Elements
23.2 The Inner Transition Elements
23.3 Coordination Compounds
23.4 Theoretical Basis for the Bonding and Properties of
Complexes

3. 23-3
The transition elements (dblock) and inner
transition elements (fblock) in the periodic table.

4. 23-4
Properties of the Transition Metals
All transition metals are metals, whereas main-group
elements in each period change from metal to nonmetal.
Many transition metal compounds are colored and
paramagnetic, whereas most main-group ionic compounds
are colorless and diamagnetic.
The properties of transition metal compounds are
related to the electron configuration of the metal ion.

5. 23-5
The Period 4 transition metals.

6. 23-6
Electron Configurations of
Transition Metals and their Ions
The d-block elements have the general condensed
ground-state configuration [noble gas]ns
2
(n–1)d
x
where
n= 4 to 7 and x= 1 to 10.
Periods 6 and 7 elements include the fsublevel:
[noble gas]ns
2
(n–2)f
14
(n–1)d
x
where n= 6 or 7.
Transition metals form ions through the loss of the ns
electrons before the (n –1)d electrons.

7. 23-7
Electronic Configuration of 3d series elements
The number of unpaired electrons increases in the first half of the
series and decreases in the second half, when pairing begins.

8. 23-8
Writing Electron Configurations of
Transition Metal Atoms and Ions
PROBLEM:Write condensedelectron configurations for the following:
(a)Zr; (b)V
3+
; (c)Mo
3+
.
PLAN:We locate the element in the periodic table and count its
position in the respective transition series. These elements are
in Periods 4 and 5, so the general electron configuration is
[noble gas]ns
2
(n–1)d
x
. For the ions, we call that nselectrons
are lost first.
SOLUTION:
(a)Zr is the second element in the 4dseries:
[Kr]5s
2
4d
2

9. 23-9
Sample Problem 23.1
(b)V is the third element in the 3dseries, so its configuration is
[Ar]4s
2
3d
3
. When it forms V
3+
, it loses the two 4se
-
first, then
one of the 3de
-
:
[Ar]3d
2
(c)Mo lies below Cr in group 6B(6), so we expect the same
exception as for Cr. The configuration for Mo is therefore
[Kr]5s
1
4d
5
. Formation of the Mo
3+
ion occurs by loss of the
single 5selectron followed by two 4delectrons:
[Kr]4d
3

10. 23-10
Periodic Properties of Transition
Elements
Across a periodthe following trends are observed:
Atomic size decreases at first, then remains relatively
constant.
-The delectrons fill innerorbitals, so they shield outer electrons very
efficiently and the 4selectrons are not pulled closer by the increasing
nuclear charge.
Electronegativity and ionization energies also increase
relatively little across the transition metals of a particular
period.

11. 23-11
Trends in key atomic properties of Period 4 elements.

12. 23-12
Trends in the Properties of
Transition Metals
Within a groupthe trends also differ from those observed
for main group elements.
Atomic size increases from Period 4 to 5, but not from
Period 5 to 6.
-The extra shrinkage from the increase in nuclear charge (called
the lanthanide contraction) is roughly equal to the normal size
increase due to adding an extra energy level.
-A Period 6 element has 32 more protons than its preceding Period
5 group member instead of only 18.

13. 23-13
Trends in the Properties of
Transition Metals
Electronegativity increaseswithin a group from Period 4
to 5, then generally remains unchanged from Period 5 to
6. The heavier elements often have high EN values.
Although atomic size increases slightly down the group, nuclear
charge increases much more, leading to higher EN values.
Ionization energy values generally increase down a
transition group, also running counter to the main group
trend.
Density increases dramatically down a group since atomic
volumes change little while atomic masses increase
significiantly.

14. 23-14
Periodic properties within the transition elements.

15. 23-15
Oxidation States of Transition Metals
Most transition metals have multiple oxidation states.
Elements in Groups 8B(8), 8B(9) and 8B(10) exhibit
fewer oxidation states. The higher oxidation state is less
common and never equal to the group number.
-The +2 oxidation state is common because the ns
2
electrons
are readily lost.
The highest oxidation state for elements in Groups 3B(3)
through 7B(7) equals the group number.
-These states are seen when the elements combine with the highly
electronegative oxygen or fluorine.

16. 23-16
Aqueous oxoanions of transition elements.
Mn
2+
MnO
4
2−
MnO
4
−
+2 +6 +7
The highest oxidation state for
Mn equals its group number.
VO
4
3−
Cr
2O
7
2−
MnO
4
−
+5 +6 +7
Transition metal ions are
often highly colored.

17. 23-17
Table 23.2 Oxidation States and d-Orbital Occupancy of the
Period 4 Transition Metals
*

18. 23-18
Metallic Behavior of Transition Metals
The lowerthe oxidation state of the transition metal, the
more metallicits behavior.
Ionicbonding is more prevalent for the loweroxidation
states, whereas covalentbonding occurs more
frequently for higheroxidation states.
Metal oxides become less basic(more acidic) as the
oxidation state increases.
A metal atom in a positive oxidation state has a greater attraction
for bonded electrons, and therefore a greater effective
electronegativity, or valence-state electronegativity, than in the
zero oxidation state. This effect increases as its oxidation state
increases.

19. 23-19
Standard Electrode Potentials of Period 4 M
2+
Ions
Half-Reaction E°(
V)
Ti
2+
(aq) + 2e
−
Ti(s)
V
2+
(aq) + 2e
−
V(s)
Cr
2+
(aq) + 2e
−
Cr(s)
Co
2+
(aq) + 2e
−
Co(s)
Fe
2+
(aq) + 2e
−
Fe(s)
Mn
2+
(aq) + 2e
−
Mn(s)
Ni
2+
(aq) + 2e
−
Ni(s)
Cu
2+
(aq) + 2e
−
Cu(s)
Zn
2+
(aq) + 2e
−
Zn(s)
-1.63
-1.19
-0.91
-0.76
0.34
-0.28
-0.25
-0.44
-1.18 In general, reducing strength
decreases across the series.

20. 23-20
Color and Magnetic Behavior
Most main-group ionic compounds are colorlessand
diamagneticbecause the metal ion has no unpaired
electrons.
Many transition metal ionic compounds are highly
coloredand paramagneticbecause the metal ion has
one or more unpaired electrons.
Transition metal ions with a d
0
or d
10
configuration are
also colorless and diamagnetic.