Answer:
(a) Transition
metals or their ions are usually paramagnetic (attracted by the magnet) due to
the presence of unpaired electrons. More is the number of unpaired electrons,
more is the paramagnetic character and more is magnetic moment. Magnetic moment
in case of Transition metals arise due to the spin motion of e?.
Magnetic moment is
calculated by spin only formula 
where
=
magnetic moment, n = no. of unpaired electrons. e.g.,
Fe (III) : [Ar] 3d5
Ithasfive unpaired
electron:
(b) In transition
elements there operate two types of forces i.e.
(i)Metallic bond
forces and
(ii) Strong
covalent bond forces between the atoms due to greater number of unpaired electrons
and mutual d-d overlapping.
Both these forces
will have to be broken in order to atomize transition elements. For this, a lot
heat is required. Hence transition metals have high enthalpy of atomization.
(c) Transition
metals, ions or their aqueous solutions are usually coloured. This is due to
the presence of partially filled d-subshell (or presence of unpaired
electrons). So, unpaired electron undergo transition within the
d-subshell (d?d transition) for which small amount of energy is required from
the visible region. Thus, one colour is absorbed and the complementary colour
is emitted e.g. CuSO4.5H2O has one unpaired electron, it
adsorbs orange colour from visible region and complementary blue colour is
emitted. Hence, it looks blue in colour.
(d) (i) Transition
metals have vacant d-orbitals, so it accepts the tone pair of reactants to form
unstable intermediate compound. Therefore, it provides surface for the
adsorption of reactant and also activate them so that the reaction becomes fast
and then unstable intermedia: compound decomposes to give the product and
catalyst is regenerated.
(ii) Transition
metal act as catalyst because they provide a low energy path for the reaction
to take place by the change their oxidation state.
e.g. 
The net reaction is
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