Which of the following types of metals form the most effective catalysts?

The number of unpaired electrons in $Zn^{2+}$ is

Which ion is not coloured?

The magnetic moment of $Mn^{4+}$ ion is approximately ...... $B.M.$

The correct statement about iron includes:
$I$) The highest oxidation state of iron is $+ 6$ in $K_2FeO_4$.
$II$) The iron shows $+ 2$ oxidation state with six electrons in the $3d$ orbitals.
$III$) The common oxidation state of iron is $+ 3$ with five unpaired electrons in the $3d$ orbital.

The divalent ion of which of the following elements in an aqueous solution has a magnetic moment of $5.92 \ BM$?