In which of the following pairs are both the ions coloured in aqueous solution? [AIPMT (S) 2006] |
(At. no.: Sc = 21, Ti = 22, Ni = 28, Cu = 29, Co = 27) |
A) Ni2+, Ti3+
B) Sc3+, Ti3+
C) Sc3 , Co2+
D) Ni2+, Cu+
Correct Answer: A
Solution :
[a] \[_{28}Ni=1{{s}^{2}},2{{s}^{2}}\,2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{8}},4{{s}^{2}}\] |
\[N{{i}^{2+}}=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{{}}}\] |
\[_{22}Ti=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{2}},4{{s}^{2}}\] |
\[T{{i}^{3+}}=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{1}}\] |
\[_{21}Sc=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{1}},4{{s}^{2}}\] |
\[S{{c}^{3+}}=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}\] |
(unpaired electron in d-orbital is not possible) |
\[_{29}Cu=1{{s}^{2}},2{{s}^{2}}\,2{{p}^{6}},3{{s}^{2}}\,3{{p}^{6}}\,3{{d}^{10}},4{{s}^{1}}\] |
\[C{{u}^{+}}=1{{s}^{2}},2{{s}^{2}}2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}\] |
(complete d-orbital) |
Hence, in above ions, Ni2+ and Ti3+ ions are coloured ions in aqueous solution due to presence of unpaired electrons in d-sub-shell. |
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