V2O3: In, V2O3, the oxidation state of V is as follows
2(x)+3(−2)=0
⇒2x−6=0
⇒x=26=3
The oxidation state of V in V2O3 is +3. The vanadium is present in its lowest oxidation state. The vanadium tends to donate the pair of electrons. Hence, it is basic oxide.
V2O5: In V2O5, the oxidation state of V is as follows
2(x)+5(−2)=0
⇒2(x)−10=0
⇒x=210=5
The oxidation state of V in V2O5 is +5. The Vanadium tends to donate and accept the pair of electrons. It is amphoteric oxide.
V2O4: In V2O4, the oxidation state of V is as follows
2(x)+4(−2)=0
⇒2(x)−8=0
⇒x=28=4
The oxidation state of V in V2O4 is +4. The Vanadium is present in its other low oxidation state. The Vanadium tends to donate and accept the pair of electrons. It is amphoteric oxide and less basic than V2O3, more basic than V2O5.
So, the correct order of basicity of oxides of vanadium is V2O3>V2O4>V2O5.