Question

Among the following series of transition metal ions, how many metals ions have $d^{2}$ electronic configuration
$Fe^{4 +},V^{3 +},Sn^{2 +},Au^{3 +},Ti^{2 +},As^{3 +},Cr^{3 +},Mn^{5 +},Co^{3 +},Zr^{2 +},Cd^{2 +},Mo^{4 +},La^{2 +},Ta^{4 +},Co^{6 +},Ni^{4 +}$

Answer 1

$Ti_{22}=3d^{2}4s^{2}$ ; $Ti^{2 +}=3d^{2}$
$V_{\text{23}}=3d^{3}4s^{2}$ ; $V^{3 +}=3d^{2}$
$Cr_{24}=3d^{5}4s^{1}$ ; $Cr^{3 +}=3d^{3}$
$Mn_{25}=3d^{5}4s^{2}$ ; $Mn^{5 +}=3d^{2}$
$Zr_{40}= \, 4d^{2}5s^{2}$ ; $Zr^{2 +}= \, 4d^{2}$
$Mo_{42}= \, 4d^{5}5s^{1};Mo^{4 +}= \, 4d^{2}$