D-And F-Block Elements Ques 473
Question: Out of $ {{[TiF_6]}^{2-}},{{[CoF_6]}^{3-}},Cu_2Cl_2 $ and $ {{[NiCl_4]}^{2-}} $ of (Z of Ti = 22, Co = 27, Cu = 29, Ni = 28), the colourless species are:
Options:
A) $ Cu_2Cl_2, $ and $ {{[NiCl_4]}^{2-}} $
B) $ {{[TiF_6]}^{2-}} $ and $ Cu_2Cl_2, $
C) $ {{[CoF_6]}^{3-}} $ and $ {{[NiCl_4]}^{2-}} $
D) $ {{[TiF_6]}^{2-}} $ and $ {{[CoF_6]}^{3-}} $
Show Answer
Answer:
Correct Answer: B
Solution:
The colour exhibited by transition metal ions is due to the presence of unpaired electrons in d-orbitals which permits the d - d excitation of electrons.
In $ {{[TiF_6]}^{2-}}-Ti $ is in + 4 O.S.; $ 3d^{0} $ -colourless In $ {{[CoF_6]}^{3-}} $ -Co is in +3 O.S; $ 3d^{5} $ -coloured In $ Cu_2Cl_2 $ -Cu is in + 1 O.S.; $ 3d^{10} $ - colourless In $ {{[ NiCl_4 ]}^{2-}} $ -Ni is in + 2 O.S; $ 3d^{8} $ -coloured
