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Q.
How many out of $\left[ TiF _{6}\right]^{2-},\left[ CoF _{6}\right]^{3+}, Cu _{2} Cl _{2}$ and $\left[ NiCl _{4}\right]^{2-}$ are colourless?
Coordination Compounds
Solution:
In $\left[ TiF _{6}\right]^{2-}, Ti ^{4+}: 3 d ^{0}$, colourless; as there is no unpaired electron.
In $\left[ CoF _{6}\right]^{3-}, Co ^{3+}: 3 d ^{6}$, coloured; as there are $4$ unpaired electrons.
In $Cu _{2} Cl _{2}, Cu ^{+}: 3 d ^{10}$, colourless; as there is no unpaired electron.
In $\left[ NiCl _{4}\right]^{2-}, Ni ^{2+}: 3 d ^{8}$, coloured; as there are $2$ unpaired electrons.
Thus, among the given, two species viz. $\left[ TiF _{6}\right]^{2-}$ and $Cu _{2} Cl _{2}$ are colourless.