The atomic radii of the second and third transition series are almost the same. Why?

In d-block elements the radii of elements of third transition series are similar to those of the elements of second transition series. Give reason.

The atomic radii of the elements are almost same of which series

Transition elements act as catalysts. Why?

Account for the following trends in atomic and ionic radii of transition metals. The atomic radii of the corresponding elements in '4d' series and 5d series are virtually the same.

Compare the general characteristics of the first series of the transition metals with those of the second and third series metals. in the respective vertical columns. Give special emphasis on the following points: (i) electronic configurations (ii) oxidation states iii) Ionisation enthalpies and iv) atomic sizes.

Atomic sizes generally increase as we come down a group of the periodic table. But in the 4th group of the periodic table, Zr and Hf have almost the same atomic sizes. Why?

Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because...