The number of unpaired electrons in $Cr^{3+}$ ion is

Properties common to the elements manganese,iron,cobalt,nickel,and copper include the ready formation by them all of:
$I$. Coloured ions in aqueous solution
$II$. Oxides of nitrogen are formed on reaction with concentrated $HNO_3$
$III$. Chlorides of formula $MCl_2$ and $MCl_3$

Which of the following metal ions will have the maximum number of unpaired electrons?

Write the ground state electronic configurations of $Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu$.

Which element from the following in $+2$ oxidation state exhibits the highest magnetic moment?

The electrode potential of $M^{2+} / M$ for $3d$-series elements shows a positive value for which of the following?