Transition metals are widely used as catalysts in industrial processes. Why do the transition elements exhibit greater similarity in properties compared to main group elements along the period as well as down the group?

Explanation

In transition metals, the last electron is added to inner b-orbital. Since the outer electronic configuration remain the same for a series, they show greater similarity in properties along a period. In a group, these elements do not differ much in size. So they show greater similarity in properties in a group.