Explain giving a suitable reason for each of the following:

1. Transition metals and their compounds are generally found to be good catalysts.

2. Metal-metal bonding is more frequent for the 4d and the 5d series of transition metals than that for the 3d series.

1. We know, transition elements show variable oxidation states in their compounds as there is a very small energy difference or almost the same energy difference in between ‘(n-1)d’ and ‘ns’ orbitals.

Transition metals and their compounds function as catalysts because of their ability to change oxidation states as they can lend electrons or withdraw electrons from the reactant, depending on the nature of the reaction. Due to this ability to interchange between the oxidation states and forming complexes with the reactants and serving as a good source for electrons make these transition metals good catalysts.

2. 3d elements have smaller atomic size compared to the 4d and the 5d series of transition metals. Due to this small size, valence electrons are not available for metal-metal bonding.

But, in 4d and 5d series transition elements, the valence electrons are not strongly held as the valence electrons are at a greater distance from the nucleus. Hence they contribute more to metal-metal bonding, as compared to transition metals of 3d series.