Question

Which of the following pairs has both the ions coloured in aqueous solution?
[Atomic numbers of $S c=21, T i=22, N i=28, C u=29, M n=25$ ]

• A. $Sc ^{3+}, Mn ^{2+}$
• B. $Ni ^{2+}, Ti ^{4+}$
• C. $Ti ^{3+}, Cu ^{+}$
• D. $Mn ^{2+}, Ti ^{3+}$

Answer 1

Answer: (D)

$Sc =21, Sc ^{3+}=[ Ar ] 3 d ^{0} 4 s ^{0}=$ no unpaired electrons
$Ti =22, Ti ^{3+}=[ Ar ] 3 d ^{1} 4 s ^{0}=1$ unpaired electron
$Ti ^{4+}=[ Ar ] 3 d ^{\circ} 4 s ^{\circ}$ no unpaired electrons
$Ni =28, Ni ^{2+}=[ Ar ] 3 d ^{8} 4 s ^{2}=2$ unpaired electrons
$Cu =29, Cu ^{+}=[ Ar ] 3 d ^{10} 4 s ^{0}=$ no unpaired electrons
$Mn =25, Mn ^{2+}=[ Ar ] 3 d ^{5} 4 s ^{2}=5$ unpaired electrons