Which of the following arrangements does not represent the correct order of the property stated against it ?

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

${Ni}^{2 +} < {Co}^{2 +} < {Fe}^{2 +} < {Mn}^{2 +}$ : ionic size

${Co}^{3 +} < {Fe}^{3 +} < {Cr}^{3 +} < {Sc}^{3 +}$ : stability in aqueous solution

$Sc < Ti < Cr < Mn :$ umber of oxidation states

$V^{2 +} < {Cr}^{2 +} < {Mn}^{2 +} < {Fe}^{2 +}$ : paramagnetic behaviour

answer is A.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

(a)
$V = 3 d^{3} 4 s^{2}; V^{2 +} = 3 d^{3} = 3 unpaired electrons Cr = 3 d^{5} 4 s^{1}; {Cr}^{2 +} = 3 d^{4} = 4 unpaired electrons Mn = 3 d^{5} 4 s^{2}; {Mn}^{2 +} = 3 d^{5} = 5 unpaired electrons Fe = 3 d^{6} 4 s^{2}; {Fe}^{2 +} = 3 d^{6} = 4 unpaired electrons$
Hence the correct order of paramagnetic behaviour
$V^{2 +} < {Cr}^{2 +} = {Fe}^{2 +} < {Mn}^{2 +}$
(b) For the same oxidation state, the ionic radii generally decreases as the atomic number increases in a particular transition series. hence the order is ${Mn}^{+ +} > {Fe}^{+ +} > {Co}^{+ +} > {Ni}^{+ +}$
(c) In solution, the stability of the compound depends upon electrode potentials, SEP of the transitions metal ions are given as
${Co}^{3 +} / Co = + 1 .97, {Fe}^{3 +} / Fe = + 0 .77 {Cr}^{3 +} / {Cr}^{2 +} = - 0 .41, {Sc}^{3 +} is highly stable as it does not show + 2 O.S.$

(d)
$Sc - (+ 2), (+ 3) Ti - (+ 2), (+ 3), (+ 4) Cr - (+ 1), (+ 2), (+ 3), (+ 4), (+ 5), (+ 6) Mn - (+ 2), (+ 3), (+ 4), (+ 5), (+ 6), (+ 7) i.e. Sc < Ti < Cr = Mn$