Question

In which of the following paris both the ions are coloured in aqueous solution? (Atomic number, `Sc - 21, Ti = 22, Ni = 28, Cu = 29, Co = 27)`
A. `Ni^(2+), Ti^(3+)`
B. `Sc^(3+),Ti^(3+)`
C. `Sc^(3+),Co^(2+)`
D. `Ni^(2+),Cu^(+)`

Answer 1

Correct Answer - A
`._(28)Ni=1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6)3d^(8),4s^(2)`
`Ni^(2+)=1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)3d^(8)`

`._(22)Ti=1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6)3d^(2),4s^(2)`
`Ti^(3+) = 1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6)3d^(1)` (1 unpaired electron)
`._(21)Sc=1s^(2),2s^(2)2p^(6),3s^(2)3p^(6)3d^(1),4s^(2)`
`Sc^(3+) = 1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)` (no unpaired electron)
`._(29)Cu= 1s^(2), 2s^(2)2p^(6), 3s^(2)3p^(6)3d^(10),4s^(1)`
`Cu^(+) = 1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)3d^(10)` (no unpaired electron)
Hence, in the above ions `Ni^(2+)`and `Ti^(3+)` are coloured in aqueous solution due to the presence of unpaired electrons in d subshell.