The correct order of the spin –only… - JEE Main 2019 Chemistry PYQ | PrepForBharat

JEE Main 2019 — Chemistry Inorganic Chemistry

2019mcqmedium

The correct order of the spin –only magnetic moment of metal ions in the following low-spin complexes, ${[V{(CN)}_{6}]}^{4-},{[Fe{(CN)}_{6}]}^{4-},{[Ru{(N{H}_{3})}_{6}]}^{3+}$ and ${[Cr{(N{H}_{3})}_{6}]}^{2+},$ is:

Official previous-year question

Held on 8 Apr 2019 · Verified 6 Jul 2026.

Options

A
${ V}^{2}+>C{r}^{2+}>R{u}^{3+}>F{e}^{2+}$
B
$C{r}^{2+}>{V}^{2}+>R{u}^{3+}>F{e}^{2+}$
C
$C{r}^{2+}>R{u}^{3+}>F{e}^{2+}>{V}^{2+}$
D
${V}^{2+}>R{u}^{3+}>C{r}^{2+}>F{e}^{2+}$

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Solution

(i) ${V}^{+2}(23)\Longrightarrow [Ar]3{d}^{3}4{d}^{0}\Longrightarrow$ JEE Main 2019 Chemistry, Coordination Compounds — solution figure 1 $(n=3)$ $\Rightarrow \mu \sqrt{3(3+2)}=3.87$

(ii) $C{r}^{+2}(24)\Longrightarrow [Ar]3{d}^{4}$ JEE Main 2019 Chemistry, Coordination Compounds — solution figure 2 $(n=2)$ $\Rightarrow \mu \sqrt{2(2+2)}=2.82$

(iii) $R{u}^{+3}(44)\Longrightarrow [kr]4{d}^{5}$ JEE Main 2019 Chemistry, Coordination Compounds — solution figure 3 $(n=1)$ $\Rightarrow \mu \sqrt{1(1+2)}=3$

(iv) $F{e}^{+2}(26) \Longrightarrow [Ar]3{d}^{6}$ JEE Main 2019 Chemistry, Coordination Compounds — solution figure 4 $(n=0)$ $\Rightarrow \mu =0$

Order of magnetic moment will be $\propto$ no. of unpaired ${e}^{-}$

${V}^{+2}> C{r}^{+2}>R{u}^{+3} >F{e}^{+2}$

$\mu =\sqrt{n(n+2)}$ B.M. Hence more the value of $n$ more will be magnitude moment.

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