Which one of the following complexes will exhibit the least paramagnetic behaviour ? [Atomic number, $$\mathrm{Cr}=24, \mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27$$]

If an iron (III) complex with the formula $$\left[\mathrm{Fe}\left(\mathrm{NH}_3\right)_x(\mathrm{CN})_y\right]^-$$ has no electron in its $$e_g$$ orbital, then the value of $$x+y$$ is

The number of unpaired d-electrons in $$\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$$ is ________.

A first row transition metal in its +2 oxidation state has a spin-only magnetic moment value of $$3.86 \mathrm{~BM}$$. The atomic number of the metal is