AQA A-level Chemistry: Transition Metals - Complex Ions

What Is A Complex Ion?

A central transition metal that is surrounded by co-ordinately bonded ligands.

Define Ligand.

An ion, atom, or molecule that has at least one lone pair of electrons.

What Are The Different Types Of Ligands?

1. Monodnetate/Unidentate
2. Bidentate
3. Polydentate

What Are Monodentate/Unidentate Ligands?

Ligands with only one lone pair of electrons and so can form only one coordinate bond with a central ion.

Give Examples For Monodentate/Unidentate Ligands.

H2O**:** (small)

**:**NH3 (small)

**:**Cl- (large)

What Are Bidentate Ligands?

Ligands which have two lone pairs of electrons and so can from two coordinate bonds with the central ion.

Give Examples For Bidentate Ligands.

Ethanedioate

Ethane-1,2-diamine

What Are Polydentate/Multidentate Ligands? What Is An Example Of One?

Ligands which can form more than two coordinate bonds.

Example: EDTA4- (Can form six coordinate bonds).

What Determines The Shape Of A Complex Ion?

1. The size of the ligands.
2. The number of coordinate bonds / coordination number.

Cl- Is An Example Of A Larger Ligand. How Many Of Them Can Fit Around A Central Metal Ion?

Four.

H2O and NH3 Are Examples Of Small Ligands. How Many Of Them Can Fit Around A Central Metal Ion?

Six.

Ethanedioate And Ethane-1,2-diamine Are Examples Of Even Larger Ligands. How Many Can Fit Around A Central Metal Ion?

Typically three.

What Are The Different Shapes Of Complex Ions?

1. Octahedral
2. Tetrahedral
3. Square planar
4. Linear

When Is A Complex Ion Octahedral?

When they have a coordination number of six.

What Are The Bond Angles Of An Octahedral Complex Ion?

90°

When Is A Complex Ion Tetrahedral/Square Planar?

When they have a coordination number of four.

What Are The Bond Angles Of A Tetrahedral Complex Ion?

109\.5°

What Are The Bond Angles Of A Square Planar Complex Ion?

90°

When Do Complex Ions Have A Linear Shape?

When they have a coordination number of two.

What Is An Example Of A Linear Complex Ion?

\[Ag(NH3)2\]+(aq), or Tollen’s reagent

What Are The Bond Angles Of A Linear Complex Ion?

180°

Formula For Working Out The Oxidation State Of A Metal Ion In A Complex.

Oxidation State Of Metal = Total oxidation state - Total oxidation state of ligands

Work Out The Oxidation State Of Copper In \[Cu(Cl4)\]2-.

Overall Charge: -2

Total charge of ligands: -4 (Cl = -1)

Ox. State Of Cu = -2 - (-4) = **+2**