i. Actually the ionic radius tends to decrease for metals (including transition metals) with increasing atomic number as they lose electrons, in other words as they lose there outer shell electron but for the non metals the ionic radius increases with increasing atomic number as they gain electrons but since they only increase with a very very small amount, it can be considered as negligible. So therefore we can conclude by saying that the overall trend of the ionic radius is decreasing across a period.

ii.Transition elements have tendency to formcomplexesmore than s and p block elements, which form only a few complexes.

The reason is :-

They have small , highly charged ions.

They have vacant low energy orbitals to accept lone pairs of electrons donated by other groups or ligand .

So they are able to form complexes with the groups which are able to donate an electron pair . These groups are known asligands.

iii. Transition metals show catalytic behavior mainly due to the following reasons: The presence of vacant d orbitals. They have the ability to exhibit variable valencies. They have a tendency to form complex compounds.