Short Answer TypeHow would you account for the following?
(i) Transition metals exhibit variable oxidation states.
(ii) Zr (Z = 40) and Hf (Z = 72) have almost identical radii.
(iii) Transition metals and their compounds act as catalyst(i) The variable oxidation states of transition elements are due to the participation of ns and (n-1) d-electrons in bonding. Lower oxidation state is exhibited when ns-electrons take part in bonding. Higher oxidation states are exhibited when (n-1) d-electrons take part in bonding.
(ii) This is because the atomic radii of 4d and 5d transition elements are nearly same. This similarity in size is a consequence of lanthanide contraction. Because of this lanthanide contraction, the radii of Hf becomes nearly equal to that of Zr.
(iii) Transition elements act as a good catalyst in chemical reaction because they can lend electrons or withdraw electrons from the reagent, depending on the nature of the reaction. The ability of transition metals to be in a variety of oxidation states, the ability to interchange between the oxidation states and the ability to form complexes with the reagents and be a good source for electrons make transition metals good catalysts.
Name the two groups into which phenomenon of catalysis can be divided. Give an example of each group with the chemical equation involved.
Explain the following giving an appropriate reason in each case.
O2 and F2 both stabilise higher oxidation states of metals but O2 exceeds F2 in doing so.
Explain the following giving an appropriate reason in each case.
Structures of Xenon fluorides cannot be explained by Valence Bond approach.
How would you account for the following?
i) Many of the transition elements are known to form interstitial compounds.
ii)The metallic radii of the third (5d) series of transition metals are virtually the same as those of the corresponding group member of the second (4d) series.
iii) Lanthanoids from primarily +3 ions, while the actinoids usually have higher oxidation states in their compounds, +4 or even + 6 being typical.
Assign reasons for the following:
(i) Copper (I) ion is not known in aqueous solution.
(ii) Actinoids exhibit greater range of oxidation states than Lanthanoids.
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