In $[NiCl_4]^{2-}$,the number of unpaired electrons is

The paramagnetic complex ion which has no unpaired electrons in $t_{2g}$ orbitals is

$[Co(C_2O_4)_3]^{3-}$ is a :

Which of the following has a square planar shape?

Which ion has tetrahedral geometry:

Using valence bond theory,explain the following in relation to the complexes given below: $[Mn(CN)_{6}]^{3-}, [Co(NH_{3})_{6}]^{3+}, [Cr(H_{2}O)_{6}]^{3+}, [FeCl_{6}]^{4-}$
$(i)$ Type of hybridisation.
$(ii)$ Inner or outer orbital complex.
$(iii)$ Magnetic behaviour.
$(iv)$ Spin only magnetic moment value.