Arrange the following metal complex / compounds in the increasing order of spin only magnetic moment. Presume all the three, high spin system. (Atomic numbers $\mathrm{Ce}=58, \mathrm{Gd}=64$ and $\mathrm{Eu}=63$.) (a) $\left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{Ce}\left(\mathrm{NO}_{3}\right)_{6}\right]$ (b) $\mathrm{Gd}\left(\mathrm{NO}_{3}\right)_{3}$ and (c) $\mathrm{Eu}\left(\mathrm{NO}_{3}\right)_{3}$ Answer is:

JEE Main · 2021 · 16 Mar 2021 · Shift 2 · d and f Block Elements

Arrange the following metal complex / compounds in the increasing order of spin only magnetic moment. Presume all the three, high spin system.
(Atomic numbers

Ce = 58, Gd = 64

and

Eu = 63

.)
(a)

(NH_{4})_{2} [Ce (NO_{3})_{6}]

(b)

Gd (NO_{3})_{3}

and
(c)

Eu (NO_{3})_{3}

Answer is:

(A)(a) $<$ (c) $<$ (b)✓ Correct
(B)(b) $<$ (a) $<$ (c)
(C)(c) $<$ (a) $<$ (b)
(D)(a) $<$ (b) $<$ (c)

Answer: (A)

Solution

(N H_{4})_{2} [Ce (N O_{3})_{6}]

two ammonium ions and six nitrate ions force cerium into the

+ 4

state, and

C e^{4 +}

4 f^{0}

with no unpaired electron, so

μ = 0

. In their nitrates gadolinium and europium are both tripositive:

G d^{3 +}

4 f^{7}

with seven unpaired electrons and

E u^{3 +}

4 f^{6}

with six. Putting these into

μ = n (n + 2)

gives

7.94

BM for gadolinium and

6.93

BM for europium. The increasing order of spin only magnetic moment is ammonium hexanitratocerate, then europium nitrate, then gadolinium nitrate.

JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Single correct option

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JEE Main · 2021 · 16 Mar 2021 · Shift 2 · d and f Block Elements

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