Formation and shape of complex ions

What is a ligand

A molecule or ion which can donate a pair of electrons to the transition metal ion forming a co-ordinate bond

What is a complex ion

A transition metal ion bonded to ligands by co-ordinate bonds

What is co-ordination number

The total number of coordinate bonds formed between the metal ion and ligands

What is a unidentate ligand

They form one co-ordinate bond

What are the most common unidentate ligands

• Water, H₂O

• Ammonia, NH₃

• Chloride, Cl^-

• Hydroxide, OH^-

• Cyanide, CN^-

What is a bidentatae ligand

They form two co-ordinate bonds for example, ethane-1-2-diamene, H₂NCH₂CH₂NH₂

What is a multidentate ligand

They form several co-ordinate bonds   

What are the common shapes ligands form

Coordination number	Shape	Example
2	Linear	[Ag(NH3)2]+[Ag(NH_3)_2]^+
4	Tetrahedral	[CoCl4]2−[CoCl_4]^{2-}
4	Square planar	[Pt(NH3)2Cl2][Pt(NH_3)_2Cl_2]
6	Octahedral ⭐	[Co(NH3​)6​]3+

Draw an octahedral shaped ion and what are the bond angles

90^o