The d and f Block Elements - III.pdfxnx vndnanf

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1. Magnetic properties
Most of the transition metals are
paramagnetic in nature due to the presence
of unpaired electrons in d-subshell.
Paramagnetismincreases with increase in
number of unpaired electrons.
Where n is the no of unpaired electrons .

2. Formation of coloured ions
Most of the compounds of transition metals are
coloured in the solid form or in solution . The
colour of transition metal compound may be
attributed to the presence of incomplete
(n-1)d subshell.
When an electron from lower energy d –orbital
is excited to a higher energy d –orbital. The
energy of excitation corresponds to the
frequency of light absorbed. This is called d-d
transition. This frequency lies in the visible
region and the colour corresponds to the
complementary colour of the light absorbed.

3. Complex formation
It is due to :-
a)Small size of the atoms and ions of transition
metals.
b)High nuclear charge.
c) Availability of vacant d-orbitalsof suitable
energy to accept lone pair of electrons
donated by ligands.

4. Interstitial Compounds
Interstitial compounds are those which are formed
when small atoms like H, C or N are trapped inside
the crystal lattice of metals. They are usually non-
stoichiometricand are neither typically ionic nor
covalent.
Ex-TiC, Fe
3H , VH
0.13etc.
They have high melting points , higher than those
of pure metals.
They are chemically inert.
They retain metallic conductivity.
They are very hard , some borides approach
diamond in hardness.

5. Alloy formation
Transition metals form a large number of
alloys. It is due to their similar atomic sizes
.Due to this, atoms of one metal can easily
take up the position in the crystal lattice of
the other .

6. Electrode potential and stability of
transition metal ions in different
oxidation state in solution
In solution the stability of a particular
oxidation state depends upon electrode
potential rather than ∆
iH.

7. Smaller the sum of total energy change for a particular oxidation state in aq
solution , greater will be the stability of that oxidation state .
or
Lower the electrode potential more stable is the O.S. in aqsolution .

8. For M
2+/
M
*There is irregular variation in electrode potential
due to irregular variation in ionisation enthalpy
(IE
1+IE
2),sublimation energy and hydration
enthalpy .
*E
o
for Mnand Zn are more –vedue to stability
of half filled d –subshell(d
5
) in Mnand fully
filled (d
10
) in Zn
2+
.
*Negative value of E
o
for Ni is due to its high
–veenthapyof hydration .
*E
o
M
2+/
M for Cu is +vebecause of its high
enthalpy of atomisation and low hydration
enthalpy .

9. For M
3+
/M
2+
* The low value for Sc reflects the stability of
Sc
3+
, which has noble gas configuration .
*The comparatively high value for Mnshows
that Mn
2+
(d
5
) is stable .
*The low value for Fe shows the extra stability
of Fe
3+
.
*The low value for V is related to the stability
of V
2+
( half filled t2g level ) .

10. Q-d
1
configuration is very unstable in ions. Why ?
Ans–After the loss of ns e-d
1
electron is easily
lost to give a stable configuration .
Q –Which is stronger reducing agent Cr
2+
or Fe
2+
in
water and why ?
Ans–Cr
2+
is stronger reducing agent than Fe
2+
because in case of Cr
2+
to Cr
3+
the change in
cofigurationis d
4
to d
3
and in case of Fe
2+
to
Fe
3+
the change d
6
to d
5
.
In medium like water d
3
is more stable
as compared to d5 due to half fillledt2g
configuration .

11. Q-Why Zn
2+
salts are white while Ni
2+
salts are
blue ?
Ans–Zn
2+
has completely filled d –orbitals
(d
10
) while Ni
2+
has incompletely filled d orbitals
(d
8
).
Q-Co
2+
is stable in aqueous solution but in the
presence of complexingagent ,it is easily
oxidised .Why ?
Ans-In the presence of complexingagent
,oxidation state of Co changes from +2 to +3
due to CFSE which is more and compensate
the ∆
iH
3.

12. Q-The 4d and 5d series of transition metal
metals have more frequent metal –metal
bonding in their compounds than 3d
series .Explain .
Ans–In the same group of d-block
elements ,the 4d and 5d transition
elements have larger size than that of
3d element .Thus the valence electrons
are less tightly held and hence can form
metal metalbond more frequently .

13. Q-E
0
for Mn
3+
/Mn
2+
is more positive than for
Fe
3+
/Fe
2+
.Why ?
Ans–Mn
3+
has the configuration 3d
4
while
that of Mn
2+
is 3d
5
.So Mn
3+
easily undergo
reduction to Mn
2+
having stable 3d
5
configuration resulting in higher value of
standard reduction potential .
Fe
3+
is more stable than Fe
2+
because of
having 3d
5
configuration and reduction to
Fe
2+
will not be easy resulting in the
decreased value of E
0
.