JEE Main 2025 Jan 28 Shift 1, Chemistry Q11: Colour, Magnetism And Stability Of Co-ordination Compounds

JEE Main2025Jan 28, Shift 1Chemistry

The metal ion whose electronic configuration is not affected by the nature of the ligand and which gives a violet colour in non-luminous flame under hot condition in borax bead test is

A
Ti $^{3 +}$
B
Ni $^{2 +}$
C
Mn $^{2 +}$
D
Cr $^{3 +}$

Solution

Ni $^{2 +}$ has the configuration [Ar] $3 d^{8}$ . In an octahedral field it gives $t_{2 g}^{6} e_{g}^{2}$ , which has the same orbital occupancy irrespective of whether the ligand is strong-field or weak-field, since the splitting cannot rearrange electrons further without changing the spin state, and Ni $^{2 +}$ remains the same in either case.

The borax bead test on Ni $^{2 +}$ in the oxidising (non-luminous) flame at high temperature gives a characteristic violet/brown bead due to nickel metaborate.

$∴$ The answer is Ni $^{2 +}$ .

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JEE Main 2025 Jan 28 Shift 1, Chemistry Q11: Colour, Magnetism And Stability Of Co-ordination Compounds

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