The d-block of the periodic table contains the elements
of the groups 3-12 in which the d orbitals are
progressively filled in each of the four long periods.
The f-block consists of elements in which 4 f and 5 f
orbitals are progressively filled. They are placed in a
separate panel at the bottom of the periodic table. The
names transition metals and inner transition metals
are often used to refer to the elements of d-and
f-blocks respectively.
There are mainly four series of the transition metals,
3d series (Sc to Zn), 4d series (Y to Cd), 5d series (La
and Hf to Hg) and 6d series which has Ac and elements
from Rf to Cn. The two series of the inner transition
metals; 4f (Ce to Lu) and 5f (Th to Lr) are known as
lanthanoids and actinoids respectively.
Originally the name transition metals was derived
from the fact that their chemical properties were
transitional between those of s and p-block elements.
Now according to IUPAC, transition metals are defined
as metals which have incomplete d subshell either in
neutral atom or in their ions. Zinc, cadmium and
mercury of group 12 have full d
10
configuration in their
ground state as well as in their common oxidation states
and hence, are not regarded as transition metals.
However, being the end members of the 3d, 4d and 5d
transition series, respectively, their chemistry is studied
along with the chemistry of the transition metals.
The presence of partly filled d or f orbitals in their
atoms makes transition elements different from that of
The
d
- and
f
-
Block Elements
The
d-
and
f-
Block Elements
After studying this Unit, you will be
able to
• learn the positions of the d– and
f-block elements in the periodic
table;
• know the electronic configurations
of the transition (d-block) and the
inner transition (f-block) elements;
• appreciate the relative stability of
various oxidation states in terms
of electrode potential values;
• describe the preparation,
properties, structures and uses
of some important compounds
such as K
2
Cr
2
O
7
and KMnO
4
;
• understand the general
characteristics of the d– and
f–block elements and the general
horizontal and group trends in
them;
• describe the properties of the
f-block elements and give a
comparative account of the
lanthanoids and actinoids with
respect to their electronic
configurations, oxidation states
and chemical behaviour.
Objectives
Iron, copper, silver and gold are among the transition elements that
have played important roles in the development of human civilisation.
The inner transition elements such as Th, Pa and U are proving
excellent sources of nuclear energy in modern times.
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