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Chemistry · 2025 · 3 marks
The d-and f-Block ElementsGeneral Properties of the Transition Elements (d-Block)3 marksUnderstandshort answer
CBSE 2025 · Region 2 · Set 2 · Q24
(a) Of the d^4 species, Cr^2+ is strongly reducing while Mn^3+ is strongly oxidising. Why? (b) Write two consequences of lanthanoid contraction. (c)…
(a)
Of the $\displaystyle \mathrm{d}^{4}$ species, $\displaystyle \mathrm{Cr}^{2+}$ is strongly reducing while $\displaystyle \mathrm{Mn}^{3+}$ is strongly oxidising. Why ?
(b)
Write two consequences of lanthanoid contraction.
(c)
Which element of 3d series has lowest enthalpy of atomisation and why ?
Marking-scheme solution
(a)
Because Mn²⁺ is more stable due to stable 3d⁵ configuration whereas Cr³⁺ is more stable due to stable t₂g³ configuration.
(b)
Similar atomic radii of 4d and 5d series elements
Separation of lanthanoids becomes difficult.
(c)
Zinc, due to weak interatomic interactions / Weak metallic bond.
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