Sc	Ti	V		Cr	Mn	Fe	Co	Ni	Cu
+1
+2			[V(H2O)6]^2+		[Cr(H2O)6]^2+
+3			[V(H2O)6]^3+		[Cr(H2O)6]^3+
+4			[VO(H2O)5]^2+		CrO4^2-
+5			VO3^-	VO2^+
+6					Cr2O7^2-
+7

V - reduction by zinc in acid solution

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

H2O

[Cr(H2O)6]^3+

[Co(H2O)6]^2+

[Cu(H2O)6]^2+

NH3

[Cr(NH3)6]^3+

[Co(NH3)6]^2+

[Co(NH3)6]^3+

Cl

[CuCl4]^2-

NaOH

Blue

Green

Violet

Purple

Pink

Orange

Yellow

Pale yellow

Yellow/green

Dark brown

---