Name the oxometal anions of the first series of transition metals in which the metal exhibits the oxidation state equal to its group number.

Explanation

i) `Cr_2O_7^(2-) and CrO_4^(2-)` (group no = oxidation state of Cr =6)
ii) `MnO_4^-` (group no. = oxidation state of Mn=7)
iii) `VO_3^-` (group no = oxidation state of V=5)