The ability of oxygen to form multiple bonds to metals explains its
superiority In the covalent oxide Mn2O7, each Mn is tetrahedrally
surrounded by O’s including a Mn–O–Mn bridge The tetrahedral [MO4]
n-
ions are known for V
V, Cr
Vl, Mn
V, Mn
Vl and Mn
VII + 7
Mn2O7
+ 6
CrO3
+ 5
V2O5
+ 4
TiO2
V2O4
CrO2
MnO2
+ 3
Sc2O3
Ti2O3
V2O3
Cr2O3
Mn2O3
Fe2O3
Mn3O4
*
 Fe3O4
*
Co3O4
*
+ 2
TiO
VO
(CrO)
MnO
FeO
CoO
NiO
CuO
ZnO
+ 1
Cu2O
Table 4