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Chemistry · 2026 · 2 marks
The d-and f-Block ElementsGeneral Properties of the Transition Elements (d-Block)2 marksUnderstandvery short answer
CBSE 2026 · Region 2 · Set 1 · Q19
(a) First ionization enthalpy of Cr is lower than that of Zn. Why? 1 + 1 (b) Mention any one property of the transition elements which makes them…
(a)
First ionization enthalpy of Cr is lower than that of Zn. Why ? $\displaystyle 1$ + $\displaystyle 1$
(b)
Mention any one property of the transition elements which makes them good catalysts.
Marking-scheme solution
(a)
Because Cr has unpaired 4s electron therefore requires lesser energy while Zn
has paired 4s electron, so requires more energy. / Because loss of one electron
gives stable 3d5 configuration in Cr whereas Zn has high ionisation enthalpy
because electron has to be removed from paired 4s electrons.
(b)
They show variable oxidation states / large surface area / vacant d-orbitals /
complex formation.
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.