\(Cr ( VI )=[ Ar ]^{18} 3 d ^0\)
\(Mn ( VII )=[ Ar ]^{18} 3 d ^0\)
\(Fe ( III )=[ Ar ]^{18} 3 d ^5\)
\(Ti ( III )=[ Ar ]^{18} 3 d ^1\)
\(V ( IV )=[ Ar ]^{18} 3 d ^1\)
Hence \(Cr\) (VI) and \(Mn\) (VII) have same \(d^0\) configuration.
$[M$ એ લેન્થેનોઈડ ધાતુ છે.]