Question

Amongst $TiF_{6}^{2 -},CoF_{6}^{3 -},Cu_{2}Cl_{2}$ and $NiCl_{4}^{2 -}$, which are the colourless species? (atomic number of Ti = 22, Co = 27, Cu = 29, Ni = 28)

• A. $CoF_{6}^{3 -}$ and$NiCl_{4}^{2 -}$
• B. $TiF_{6}^{2 -}$ and $Cu_{2}Cl_{2}$
• C. $Cu_{2}Cl_{2}$ and$NiCl_{4}^{2 -}$
• D. $TiF_{6}^{2 -}$ and $CoF_{6}^{3 -}$

Answer 1

Answer: (B)

$TiF_{6}^{2 -}$ and $Cu_{2}Cl_{2}$

Answer 2

In $TiF_{6}^{2 -}$ titanium is in +4 oxidation state in $Cu_{2}Cl_{2},$ the copper is in +1 oxidation state. Thus in both cases, transition from one d- orbital to other is not possible

$Ti - 3d^{2},4s^{2} \rightarrow Ti^{4 +} - 3d^{0}4s^{0}$

$Cu - 3d^{10},4s^{1} \rightarrow Cu^{1 +} - 3d^{10}4s^{0}$