Electrons in a paramagnetic compound are

Among $VO_2^{+}$,$MnO_4^{-}$ and $Cr_2O_7^{2-}$,the spin-only magnetic moment value of the species with least oxidising ability is $BM$ (Nearest integer). (Given atomic number $V=23$,$Mn=25$,$Cr=24$)

Explain geometrical isomerism in four-coordinated compounds.

The correct order of the spin only magnetic moment of metal ions in the following low spin complexes,$[V(CN)_6]^{4-}$,$[Fe(CN)_6]^{4-}$,$[Ru(NH_3)_6]^{3+}$,and $[Cr(NH_3)_6]^{2+}$,is

In $[Cr(C_2O_4)_3]^{3-}$,the isomerism shown is :-

Which one of the following compounds is not coloured?