DAY TWENTY SEVEN
The d - and f - Block
Elements
Learning & Revision for the Day
u d-Block Elements u f-Block Elements
u Some Important Compounds of (Inner Transition Elements)
Transition Elements
In d-block elements last electron enters in penultimate (n − 1) d-orbital while in f -block
elements last electron enters in (n − 2) f -orbital.
d-Block Elements
d-block elements are present from fourth period onwards. There are mainly three series of the
transition metals, (a) 3d-series (Sc to Zn), (b) 4d-series (Y to Cd) and (c) 5d-series (La to Hg,
omitting Ce to Lu).
d-block elements are known as transition elements because of their position in the periodic
table is between the s-block and p-block elements.
Electronic Configuration
Electronic configuration of the transition elements is (n − 1) d1 − 10 ns1 − 2 . [(n − 1) d10 ], these are
d-block elements, but Zn, Cd and Hg are not transition metals because these have
completely filled d-orbitals.
Transition Metals or d-block Elements
3rd group 4th group 5th group 6th group 7th group
ns2 (n − 1)d 1 ns2 (n − 1)d 2 ns2 (n − 1)d 3 ns1 (n − 1)d 5 ns2 (n − 1) d 5
Sc Ti V Cr Mn
Y Zr Nb Mo Tc
La Hf Ta W Re
8th group 9th group 10th group 11th group 12th group
ns2 (n − 1) d 6 ns2 (n − 1) d 7 ns2 (n − 1) d 8 ns1 (n − 1) d 10 ns2 (n − 1) d 10
Fe Co Ni Cu Zn
Ru Rh Pd Ag Cd
Os Ir Pt Au Hg
, simple halides but MnO3 F is known and beyond Mn no
Characteristics of Transition Metals metal has a trihalide except FeX 3 and CoF3 . The increasing
Following one the important characteristics of transition order of oxidising power in the series is
metals: VO+ 2− −
2 < Cr2O7 < MnO 4 .
(i) The differentiating electron, enters in d-sub-shell.
l The highest oxidation states of transition metals are found
(ii) These have incomplete d-sub-shell orbitals either in in their compounds with fluorine and oxygen only because
ground state or in most common oxidation state. of their higher electronegativity and smaller atomic size.
(iii) All the transition metals are electropositive in nature.
6. Standard Electrode Potentials
(iv) The electronegativity and ionisation energy of transition
The transformation of the solid metal atoms to M 2+ ions in
metals are more than of s-block elements but less, than of
solution is their standard electrode potentials. If sum of the
p-block elements, thus are called transition elements.
first and second ionisation enthalpies is greater than
(v) These show variable oxidation states due to involvement hydration enthalpy, standard potential (E ° 2+ ) will be
of ns and (n − 1)d-electrons. M /M
positive and reactivity will be lower and vice-versa.
General Trends in Properties 7. Atomic and Ionic Radii
l In transition metals radii decreases on moving left to right
of Transition Elements in a period, because of net nuclear charge increases due to
The characteristics of d-block elements and their trends are poor shielding effect. Due to this, the atomic and ionic radii
discussed below: for transition elements for a given series show a decreasing
trend for first five elements and then becomes almost
1. Metallic Character constant for next four elements of the series. At the end of
Metallic character of transition elements in each series are the period, there is a slight increase in the atomic radii.
almost similar, all are metals due to less number of electrons l The atomic and ionic radii of the elements of 4d-series are
in outermost subshell. higher than corresponding element of 3d-series due to
increase in number of shells. However, the corresponding
2. Enthalpies of Atomisation elements of 4d-and 5d-series have almost similar values, e.g.
Transition elements exhibit higher enthalpies of atomisation Zr radii - 160 pm, Hf radii-159 pm. It is due to lanthanoid
because of large number of unpaired electrons in their atoms. contraction. Nb and Ta, Mo and W also have nearly same
Transition elements have very high melting and boiling points. size due to lanthanoid contraction.
3. Ionisation Enthalpy Coloured Ions
The values of ionisation enthalpy for 5d-series are higher than l The d-orbitals are non-degenerated in the presence of
that of 3d- and 4d-series due to weak shielding effect of 4f ligands. When an electron from a lower energy d-orbital is
electrons present in 5d-series transition elements. excited to a higher energy d-orbital (d -d* transition) the
Ionisation enthalpy values of Zn, Cd and Hg are abnormally energy of required wavelength is absorbed and rest light is
higher an account of greater stability of s-subshell. transmitted out. Therefore, the colour observed
corresponds to the complementary colour of the light
4. Oxidation States absorbed.
Transition metals show variable oxidation states due to two l In V2O 5, V is in +5 oxidation state. In spite of d° it is
incomplete outermost shells. Only stable oxidation states of coloured compound. This colour arises due to defects in
the first row transition metals are given below: the crystal lattice and charge transfer.
Sc (+3), Ti (+4), V (+5), Cr (+3, + 6), Mn(+2,+7), 8. Complex Compounds
Fe (+2,+3) Co (+2,+3), Ni (+2),Cu (+2), Zn (+2) Transition metals have small size and high nuclear charge,
l In each period, the highest oxidation state increases with which facilitate the acceptance of lone pair of electrons from
increase in atomic number, attains a maximum value in the ligands. They have vacant d-orbitals of appropriate energy in
middle and then decreases, for example, Mn (3d-series), Ru order to accommodate the lone pair of electrons.
(4 d-series) and Os (5d-series) has maximum value for
oxidation state as + 7, + 8, + 8 respectively. 9. Catalytic Properties
l The transition elements in their lower oxidation states The transition metals have incomplete outermost orbitals and
(+2 and + 3) usually forms ionic compounds. In higher ability to adopt multiple oxidation states as well as forming
oxidation state compounds are normally covalent. Ni and Fe complexes, therefore used as a catalyst. They also provide
in Ni(CO)4 and Fe(CO)5 show zero oxidation state. larger surface area for the reactant to be adsorbed.
5. Trends in Stability of Higher Oxidation States 10. Magnetic Properties
l The highest oxidation numbers are achieved in TiX 4 , l The magnetic properties of a d-block elements are due to
VF5 and CrF6. The +7 state for Mn is not represented in spin of unpaired electrons. The magnetic moment is
The d - and f - Block
Elements
Learning & Revision for the Day
u d-Block Elements u f-Block Elements
u Some Important Compounds of (Inner Transition Elements)
Transition Elements
In d-block elements last electron enters in penultimate (n − 1) d-orbital while in f -block
elements last electron enters in (n − 2) f -orbital.
d-Block Elements
d-block elements are present from fourth period onwards. There are mainly three series of the
transition metals, (a) 3d-series (Sc to Zn), (b) 4d-series (Y to Cd) and (c) 5d-series (La to Hg,
omitting Ce to Lu).
d-block elements are known as transition elements because of their position in the periodic
table is between the s-block and p-block elements.
Electronic Configuration
Electronic configuration of the transition elements is (n − 1) d1 − 10 ns1 − 2 . [(n − 1) d10 ], these are
d-block elements, but Zn, Cd and Hg are not transition metals because these have
completely filled d-orbitals.
Transition Metals or d-block Elements
3rd group 4th group 5th group 6th group 7th group
ns2 (n − 1)d 1 ns2 (n − 1)d 2 ns2 (n − 1)d 3 ns1 (n − 1)d 5 ns2 (n − 1) d 5
Sc Ti V Cr Mn
Y Zr Nb Mo Tc
La Hf Ta W Re
8th group 9th group 10th group 11th group 12th group
ns2 (n − 1) d 6 ns2 (n − 1) d 7 ns2 (n − 1) d 8 ns1 (n − 1) d 10 ns2 (n − 1) d 10
Fe Co Ni Cu Zn
Ru Rh Pd Ag Cd
Os Ir Pt Au Hg
, simple halides but MnO3 F is known and beyond Mn no
Characteristics of Transition Metals metal has a trihalide except FeX 3 and CoF3 . The increasing
Following one the important characteristics of transition order of oxidising power in the series is
metals: VO+ 2− −
2 < Cr2O7 < MnO 4 .
(i) The differentiating electron, enters in d-sub-shell.
l The highest oxidation states of transition metals are found
(ii) These have incomplete d-sub-shell orbitals either in in their compounds with fluorine and oxygen only because
ground state or in most common oxidation state. of their higher electronegativity and smaller atomic size.
(iii) All the transition metals are electropositive in nature.
6. Standard Electrode Potentials
(iv) The electronegativity and ionisation energy of transition
The transformation of the solid metal atoms to M 2+ ions in
metals are more than of s-block elements but less, than of
solution is their standard electrode potentials. If sum of the
p-block elements, thus are called transition elements.
first and second ionisation enthalpies is greater than
(v) These show variable oxidation states due to involvement hydration enthalpy, standard potential (E ° 2+ ) will be
of ns and (n − 1)d-electrons. M /M
positive and reactivity will be lower and vice-versa.
General Trends in Properties 7. Atomic and Ionic Radii
l In transition metals radii decreases on moving left to right
of Transition Elements in a period, because of net nuclear charge increases due to
The characteristics of d-block elements and their trends are poor shielding effect. Due to this, the atomic and ionic radii
discussed below: for transition elements for a given series show a decreasing
trend for first five elements and then becomes almost
1. Metallic Character constant for next four elements of the series. At the end of
Metallic character of transition elements in each series are the period, there is a slight increase in the atomic radii.
almost similar, all are metals due to less number of electrons l The atomic and ionic radii of the elements of 4d-series are
in outermost subshell. higher than corresponding element of 3d-series due to
increase in number of shells. However, the corresponding
2. Enthalpies of Atomisation elements of 4d-and 5d-series have almost similar values, e.g.
Transition elements exhibit higher enthalpies of atomisation Zr radii - 160 pm, Hf radii-159 pm. It is due to lanthanoid
because of large number of unpaired electrons in their atoms. contraction. Nb and Ta, Mo and W also have nearly same
Transition elements have very high melting and boiling points. size due to lanthanoid contraction.
3. Ionisation Enthalpy Coloured Ions
The values of ionisation enthalpy for 5d-series are higher than l The d-orbitals are non-degenerated in the presence of
that of 3d- and 4d-series due to weak shielding effect of 4f ligands. When an electron from a lower energy d-orbital is
electrons present in 5d-series transition elements. excited to a higher energy d-orbital (d -d* transition) the
Ionisation enthalpy values of Zn, Cd and Hg are abnormally energy of required wavelength is absorbed and rest light is
higher an account of greater stability of s-subshell. transmitted out. Therefore, the colour observed
corresponds to the complementary colour of the light
4. Oxidation States absorbed.
Transition metals show variable oxidation states due to two l In V2O 5, V is in +5 oxidation state. In spite of d° it is
incomplete outermost shells. Only stable oxidation states of coloured compound. This colour arises due to defects in
the first row transition metals are given below: the crystal lattice and charge transfer.
Sc (+3), Ti (+4), V (+5), Cr (+3, + 6), Mn(+2,+7), 8. Complex Compounds
Fe (+2,+3) Co (+2,+3), Ni (+2),Cu (+2), Zn (+2) Transition metals have small size and high nuclear charge,
l In each period, the highest oxidation state increases with which facilitate the acceptance of lone pair of electrons from
increase in atomic number, attains a maximum value in the ligands. They have vacant d-orbitals of appropriate energy in
middle and then decreases, for example, Mn (3d-series), Ru order to accommodate the lone pair of electrons.
(4 d-series) and Os (5d-series) has maximum value for
oxidation state as + 7, + 8, + 8 respectively. 9. Catalytic Properties
l The transition elements in their lower oxidation states The transition metals have incomplete outermost orbitals and
(+2 and + 3) usually forms ionic compounds. In higher ability to adopt multiple oxidation states as well as forming
oxidation state compounds are normally covalent. Ni and Fe complexes, therefore used as a catalyst. They also provide
in Ni(CO)4 and Fe(CO)5 show zero oxidation state. larger surface area for the reactant to be adsorbed.
5. Trends in Stability of Higher Oxidation States 10. Magnetic Properties
l The highest oxidation numbers are achieved in TiX 4 , l The magnetic properties of a d-block elements are due to
VF5 and CrF6. The +7 state for Mn is not represented in spin of unpaired electrons. The magnetic moment is
