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Answer the following.
Account for the following/Explain why: Transition metals exhibit variable oxidation states. ( ) and…
Account for the following/Explain why:
(i)[1.0]
Transition metals exhibit variable oxidation states.
(ii)[1.0]
$\text{Zr}$ ($Z = 40$) and $\text{Hf}$ ($Z = 72$) have almost identical radii.
(iii)[1.0]
Transition metals and their compounds act as a catalyst.
Answer
Answer (i)
AIBecause the energy difference between the $ns$ and $(n-1)d$ orbitals is very small, both sets of electrons take part in bonding, giving several oxidation states.
Answer (ii)
AIBecause of the lanthanoid contraction, the size decrease across the 4f series offsets the increase in size down the group, so Zr and Hf have almost identical radii.
Answer (iii)
AIBecause they show variable oxidation states and can form unstable intermediates, and have a large surface area with free valencies for adsorbing reactants, they act as catalysts.
From ISC 2018 Specimen Chemistry Paper 1, question 13(a).