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JEE Main 2025 Apr 7 Shift 1, Chemistry Q11: d-Block Elements

JEE Main2025Apr 7, Shift 1Chemistry
Q.

The number of valence electrons present in the metal among Cr, Co, Fe and Ni which has the lowest enthalpy of atomisation is

  1. A

    8

  2. B

    9

  3. C

    6

  4. D

    10

Solution

Among the four 3d metals Cr, Fe, Co and Ni, the enthalpy of atomisation correlates with the strength of metallic bonding, which depends on the number of unpaired d-electrons available for bonding. Chromium has the half-filled configuration; the lone electron and weaker metallic cohesion (compared with Fe, Co, Ni which form stronger metallic bonds via paired and unpaired d-electrons) result in the lowest enthalpy of atomisation in the set.

Configuration of Cr:

Valence electrons (3d + 4s) .

Option (3).

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