Question

$Cs\left[{AuCl}_3\right]$ is diamagnetic in nature. Is it ${Cs}^{+}{\left[{AuCl}_3\right]}^{-}$?

Answer 1

If $Cs\left[Au{Cl}_3\right]$ is written as ${Cs}^{+}{\left[{AuCl}_3\right]}^{-}$, then check whether ${\left[Au{Cl}_3\right]}^{-}$ is diamagnetic or not.

So the oxidation state of $Au$ will be $+2$ i.e, $Au$ $\left(II\right)$

Since it has one unpaired electron, it is paramagnetic not diamagnetic.

So it is not ${Cs}^{+}{\left[{AuCl}_3\right]}^{-}$.