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Chemistry · 2022 · 3 marks
The d-and f-Block ElementsGeneral Properties of the Transition Elements (d-Block)3 marksUnderstandshort answer
CBSE 2022 · Region 1 · Set 3 · Q8
(a) Account for the following: (i) Zr and Hf have almost similar atomic radii. (ii) Transition metals show variable oxidation states. (iii) Zinc has…
(a)
Account for the following :
(i)
Zr and Hf have almost similar atomic radii.
(ii)
Transition metals show variable oxidation states.
(iii)
Zinc has lowest enthalpy of atomisation.
OR
(b)
Why transition metals and their compounds act as good catalyst ? How is the variability in oxidation states of transition metals different from that of the non-transition metals ? Illustrate with examples.
Marking-scheme solution
(a)(i)
Due to lanthanoid contraction / poor shielding by 4f orbitals. (ii) Due to incomplete filling of d orbitals / participation of both (n-$\displaystyle 1$) d and ns
orbitals.
(iii)
No unpaired electrons in 3d subshell / weak metallic bonding.
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CBSE Class 12 Chemistry past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.