The green coloured complex ion of nickel in its aqueous solution is

The green coloured complex ion of nickel in its aqueous solution is
  1. $\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}$
  2. $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_2(\mathrm{en})_2\right]^{2+}$
  3. $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_4(\mathrm{en})\right]^{2+}$
  4. $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$

Solution

In complex $\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$ the strong ligand is absent. Thus, electrons do not go for pairing and two unpaired $e^{-}$are present in $\mathrm{Ni}^{2+}$ complex. Hence, is a coloured complex.

Asked in: AP EAMCET 2018 (24 Apr Shift 1)

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