Water :

Werner was able to explain the bonding in complex.

Primary valency (Pv) : This is non- directional and ionizable. In fact it is the positive charge on the metal ion.

Secondary valency (Sv) : This is directional and non- ionizable. It is equal to the number of ligand atoms co-ordinated to the metal (co-ordination number). Example :

Atom/ion/complex (1)	Configuration (2)	Oxidation state of metal (3)	Type of hybridization (4)	Geometry shape (5)	No. of unpaired electrons (6)	Magnetic nature (7)
Ni2+(d8)		+2			2	Paramagnetic
[NiCl4]2–		+2	sp3	Tetrahedral	2	Paramagnetic
[Ni(CN)4]2+		+2	dsp2	Square planar	0	Diamagnetic
Ni		0			2	Paramagnetic
Ni(CO)4		0	sp3	Tetrahedral	0	Diamagnetic
[Ni(NH3)6]2+		+2	sp3d2(outer)	Octahedral	2	Paramagnetic
Mn2+(d5)		+2			5	Paramagnetic
[Mn(CN)6]4–		+2	d2sp3(Inner)	Octahedral	1	Paramagnetic
[MnCl4]2		+2	sp3	Tetrahedral	5	Paramagnetic
Cu2+(d9)		+2			1	Paramagnetic
[CuCl4]2–		+2	sp3	Tetrahedral	1	Paramagnetic
[Cu(NH3)4]2+		+2	dsp2	Square planar	1	Paramagnetic
(1)	(2)	(3)	(4)	(5)	(6)	(7)
Cr3+(d3)		+3			3	Paramagnetic
[Cr(NH3)6]3+		+3	d2sp3 (Inner)	Octahedral	3	Paramagnetic
[Cr(H2O)6]3+		+3	sp3d2 (Outer)	Octahedral	3	Paramagnetic
CO3+(d6)		+3			4	Paramagnetic
[CoF6]3–		+3	sp3d2 (Outer)	Octahedral	4	Paramagnetic
[Co(NH3)6]3+		+3	d2sp3 (Inner)	Octahedral	0	Diamagnetic
CO2+(d7)		+2			3	Paramagnetic
[Co(H2O)6]2+		+2	sp3d2 (Outer)	Octahedral	3	Paramagnetic
Fe2+(d6)		+2			4	Paramagnetic
[Fe(CN)6]4–		+2	d2sp3 (Inner)	Octahedral	0	Diamagnetic
[Fe(H2O)6]2+		+2	sp3d2 (Outer)	Octahedral	4	Paramagnetic
[Fe(NH3)6]2+	Same	+2	sp3d2 (Outer)	Octahedral	4	Paramagnetic
Fe3+(d5)		+3		Octahedral	5	Paramagnetic
d2sp3 (Inner)		1	Paramagnetic
Fe		o			4	Paramagnetic
Fe(CO)5		o	dsp3 (Inner)	Trigonal bipyramidal	o	Diamagnetic