For a metal ion, the calculated magnetic moment is $$4.90 ~\mathrm{BM}$$. This metal ion has ___________ number of unpaired electrons.

In potassium ferrocyanide, there are ________ pairs of electrons in the $$t_{2g}$$ set of orbitals.

The observed magnetic moment of the complex $$\left.\left[\operatorname{Mn}(\underline{N} C S)_{6}\right)\right]^{x^{-}}$$ is $$6.06 ~\mathrm{BM}$$. The numerical value of $$x$$ is __________.

Number of ambidentate ligands in a representative metal complex $$\left[\mathrm{M}(\mathrm{en})(\mathrm{SCN})_{4}\right]$$ is ___________.

[en = ethylenediamine]