Quick Revision: d & f-Block Elements Notes | Study Chemistry Class 12 - NEET

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The transition elements may be defined as elements whose atoms or simple ions in their most common
oxidation state contain partially filled d-orbitals. This definition does not cover zinc, cadmium and mercury.
However, these are studied with transition elements.
The general electronic configuration of these elements is (n – 1)d
1 – 10
 ns
0 – 2
.
ATOMIC AND PHYSICAL PROPERTIES
The important properties of the transition metals are given below :
1. Metallic Character
(a) Transition elements exhibit good mechanical properties, i.e, they are hard, malleable and ductile. They
have high enthalpies of atomization, high melting and boiling points, they have high thermal and
electrical conductivity as well as lustre.
(b) Their mechanical properties and high melting as well as boiling points indicate the presence of strong
metallic bond.
2. Ionisation Energies
(a) The ionisation energies of transition metals increases as we move across each series though not
quite regularly.
(b) It is evident that first ionisation energies of most of the 5d elements are higher than those of 3d and
4d-elements. This is due to the fact that the outer valence electrons of 5d-elements experience
greater effective nuclear charge due to poor shielding of the nucleus by 4f-electrons.
3. Electrode Potential
In general, transition elements have low negative values of standard reduction electrode potential due to
high ionisation energies, high heat of sublimation which are more than offset with large heats of hydration.
Consequently, transition elements are weak reducing agents  and are less reactive than s-block
elements.
4. Variable Oxidation States
(a) Transition metals exhibit a wide range of oxidation states. When 'ns' electrons are involved, then
compounds with lower oxidation states are formed. In compounds with higher oxidation states, (n–1) d
electrons are also involved.
(b) The highest oxidation state exhibited by any transition metal is +8, i.e, Ruthenium tetroxide (RuO
4
)
and Osmium tetroxide (OsO
4
)
(c) The highest oxidation state are shown by transition metal when they combine with most
electronegative elements such as fluorine or oxygen, i.e., CrO
3
, Mn
2
O
7
 and VF
5
.