Which one of the following belongs to the $3d-$ transition series?

Explain giving reasons:
$(i)$ Transition metals and many of their compounds show paramagnetic behaviour.
$(ii)$ The enthalpies of atomisation of the transition metals are high.
$(iii)$ The transition metals generally form coloured compounds.
$(iv)$ Transition metals and their many compounds act as good catalysts.

Iron $(Fe)$ is classified as:

Among the following components of cement,which is present in the highest amount?

The electrons which take part in order to exhibit variable oxidation states by transition metals are

The atomic number of $Pd$ is $46$. The atomic numbers of the elements lying immediately above and below it in the same group are,respectively,.....................