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

Chemistry · d and f Block Elements

JEE Main 2025 — 7 April, Morning Shift — Question 6

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

Option A:
8
Option B:
10
Option C:
6
Correct
Option D:
9

Answer: C

Step-by-step solution

Enthalpy of atomisation (kJ/mol)

$\mathrm{Cr} \rightarrow 397$

$Co$ $\rightarrow 425$

$\mathrm{Fe} \rightarrow 416$

$\mathrm{Ni} \rightarrow 430$

$Cr$ has the lowest value of enthalpy of atomisation, its electronic configuration is $\mathrm{Ar}^{18} \cdot 3 d^{5} 4 s^{1}$

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Exam: JEE Main 2025
Paper: 7 April, Morning Shift
Subject: Chemistry
Chapter: d and f Block Elements
Topic: Properties of compounds of 3d Series elements + Comparison between 3d, 4d, 5d

The first transition series metal ' M ' has the highest enthalpy of atomisation in its series. One of its aquated ion ( M^ n+ ) exists in…

Answer: C

Step-by-step solution

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