JEE Main 2021 — Chemistry Inorganic Chemistry

2021mcqeasy

In which of the following order the given complex ions are arranged correctly with respect to their decreasing spin only magnetic moment?

(i) ${[{\mathrm{FeF}}_{6}]}^{3-}$

(ii) ${[\mathrm{Co}{({\mathrm{NH}}_{3})}_{6}]}^{3+}$

(iii) ${[{\mathrm{NiCl}}_{4}]}^{2-}$

(iv) ${[\mathrm{Cu}{({\mathrm{NH}}_{3})}_{4}]}^{2+}$

Official previous-year question

Held on 25 Feb 2021 · Verified 6 Jul 2026.

Options

A
$(\mathrm{ii})>(i)>(\mathrm{iii})>(\mathrm{iv})$
B
$(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})>(i)$
C
$(i)>(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})$
D
$(\mathrm{ii})>(\mathrm{iii})>(i)>(\mathrm{iv})$

Did you get this right?

Solution

Complex

(i) ${[{\mathrm{FeF}}_{6}]}^{3-}{\mathrm{Fe}}^{3+}\Rightarrow [\mathrm{Ar}]3{d}^{5},{F}^{-}$ is WFL

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 1

$n=5,\mu =\sqrt{35}B.M$

(ii) ${[\mathrm{Co}{({\mathrm{NH}}_{3})}_{6}]}^{3+}\Rightarrow {\mathrm{Co}}^{3+}[\mathrm{Ar}]3{d}^{6},{\mathrm{NH}}_{3}$ is SFL

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 2

$n=0,\mu =0B.M$

(iii) ${[{\mathrm{NiCl}}_{4}]}^{2-}{\mathrm{Ni}}^{2+}\Rightarrow [\mathrm{Ar}]3{d}^{8},{\mathrm{Cl}}^{-}\rightarrow \mathrm{WFL}$

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 3

$n=2,\mu =\sqrt{8}B.M$

(iv) ${[\mathrm{Cu}{({\mathrm{NH}}_{3})}_{4}]}^{2+}{\mathrm{Cu}}^{2+}\Rightarrow [\mathrm{Ar}]3{d}^{9},{\mathrm{NH}}_{3}\rightarrow \mathrm{SFL}$

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 4

$n=1,\mu =\sqrt{3}B.M$

Thus correct order of spin only magnetic moment is

$(i)>(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})$

Your note

JEE Main Inorganic Chemistry in other years

Inorganic Chemistry 2026 Inorganic Chemistry 2025 Inorganic Chemistry 2024 Inorganic Chemistry 2023 Inorganic Chemistry 2022 Inorganic Chemistry 2020 Inorganic Chemistry 2019 Inorganic Chemistry 2018 Inorganic Chemistry 2017 Inorganic Chemistry 2016 Inorganic Chemistry 2015 Inorganic Chemistry 2014

Keep practicing Inorganic Chemistry

Work through every JEE Main Inorganic Chemistry PYQ, year by year.

Browse all Chemistry topics

Options

$(\mathrm{ii})>(i)>(\mathrm{iii})>(\mathrm{iv})$

$(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})>(i)$

$(i)>(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})$

$(\mathrm{ii})>(\mathrm{iii})>(i)>(\mathrm{iv})$

Solution

Complex

(i) ${[{\mathrm{FeF}}_{6}]}^{3-}{\mathrm{Fe}}^{3+}\Rightarrow [\mathrm{Ar}]3{d}^{5},{F}^{-}$ is WFL

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 1

$n=5,\mu =\sqrt{35}B.M$

(ii) ${[\mathrm{Co}{({\mathrm{NH}}_{3})}_{6}]}^{3+}\Rightarrow {\mathrm{Co}}^{3+}[\mathrm{Ar}]3{d}^{6},{\mathrm{NH}}_{3}$ is SFL

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 2

$n=0,\mu =0B.M$

(iii) ${[{\mathrm{NiCl}}_{4}]}^{2-}{\mathrm{Ni}}^{2+}\Rightarrow [\mathrm{Ar}]3{d}^{8},{\mathrm{Cl}}^{-}\rightarrow \mathrm{WFL}$

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 3

$n=2,\mu =\sqrt{8}B.M$

(iv) ${[\mathrm{Cu}{({\mathrm{NH}}_{3})}_{4}]}^{2+}{\mathrm{Cu}}^{2+}\Rightarrow [\mathrm{Ar}]3{d}^{9},{\mathrm{NH}}_{3}\rightarrow \mathrm{SFL}$

JEE Main 2021 Chemistry, Coordination Compounds — solution figure 4

$n=1,\mu =\sqrt{3}B.M$

Thus correct order of spin only magnetic moment is

$(i)>(\mathrm{iii})>(\mathrm{iv})>(\mathrm{ii})$

JEE Main 2021 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry

JEE Main 2021 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry