AP | A-Level | IB | NCERT 11 + 12 – FREE NOTES, RESOURCES AND VIDEOS!
IB® (SL and AHL)
YouTube Channel
YouTube Channel
@chemistry.student
S1.1 - Introduction to the particulate nature of matter S1.2 - The nuclear atom S1.3 - Electron configurations S1.4 - Counting particles by mass - The mole S1.5 - Ideal gases S2.1 - The ionic model S2.2 - The covalent model S2.3 - The metallic model S2.4 - From models to materials S3.1 - The periodic table - Classification of elements S3.2 - Functional groups - Classification of organic compounds R1.1 - Measuring enthalpy changes R1.2 - Energy cycles in reactions R1.3 - Energy from fuels R1.4 - Entropy and spontaneity AHL R2.1 - How much? The amount of chemical change R2.2 - How fast? The rate of chemical change R2.3 - How far? The extent of chemical change R3.1 - Proton transfer reactions R3.2 - Electron transfer reactions R3.3 - Electron sharing reactions R3.4 - Electron-pair sharing reactions

S2.2 - The covalent model

2.2.1 Covalent Bonds and Lewis Formulas 2.2.2 Bond Types 2.2.3 Co-coordination (Dative) Bonds 2.2.4 VSEPR Shapes of Molecules 2.2.5 Electronegativity and Bond Polarity 2.2.6 Polarity and Dipole Moments 2.2.7 Covalent Network Structures and Allotropes 2.2.8 Intermolecular Forces 2.2.9 Physical Properties of Covalent Substances 2.2.10 Chromatography and Intermolecular Forces 2.2.11 Resonance Structures (AHL) 2.2.12 Benzene and Resonance (AHL) 2.2.13 Expanded Octet and VSEPR (AHL) 2.2.14 Formal Charge (AHL) 2.2.15 Sigma and Pi Bonds (AHL) 2.2.16 Hybridization (AHL)

Coordination (Dative) Bonds

Specification Reference S2.2.3

Quick Notes

  • A coordination bond (dative covalent bond) is a covalent bond where both electrons come from the same atom.
  • Once formed, it behaves like a normal covalent bond in terms of length and strength.
  • Represented with an arrow (→) showing electron donation.
  • Examples:
    • Ammonium ion (NH₄⁺)
    • Aluminium chloride dimer (Al₂Cl₆)
    • Transition metal complexes (e.g. [Cu(NH₃)₄]²⁺)
  • In Lewis acid–base theory:
    • Donor atom = Lewis base (electron pair donor)
    • Acceptor atom = Lewis acid (electron pair acceptor)

Full Notes

What Is a Coordination Bond?

A coordination (dative covalent) bond is a special type of covalent bond where both electrons in the bond come from the same atom.

Once formed, it is identical to a normal covalent bond in strength and length.

IB Chemistry diagram showing the arrow notation for a coordinate (dative covalent) bond.

Representation: The bond is shown by an arrow (→) pointing from the donor atom (which provides both electrons) to the acceptor atom.

Examples

IB Chemistry example of the ammonium ion NH4+ showing nitrogen donating a lone pair to hydrogen to form a coordinate bond.

Ammonium ion (NH₄⁺):
Ammonia (NH₃) donates a lone pair from nitrogen to a H⁺ ion. This forms a coordinate bond, resulting in NH₄⁺.

IB Chemistry diagram of aluminium chloride dimer Al2Cl6 showing coordinate bonds between aluminium and chlorine atoms.

Aluminium chloride (Al₂Cl₆):
Two AlCl₃ units join via coordinate bonds from Cl atoms donating lone pairs to electron-deficient Al atoms.

Identifying Coordination Bonds

To identify a coordination bond:

Transition Metal Complexes (AHL Link)

Transition metals often form coordination bonds with ligands (molecules or ions with lone pairs). This forms complex ions.

For exampleWater (H₂O) can donate a lone pair from oxygen to a metal ion.

IB Chemistry diagram of a water molecule acting as a ligand, donating a lone pair to a transition metal ion.

Often, more than one ligand can bond to the same metal ion, forming a complex ion.

For exampleSix water molecules can get close enough to a copper ion to form a hexa-aqua copper (II) ion, [Cu(H₂O)₆]²⁺.

IB Chemistry diagram of the [Cu(H2O)6]2+ complex showing six coordinate bonds formed with water ligands.

Connection to Lewis Theory

Coordination bonds can be described with Lewis acid–base theory:

This explains why transition metals can form stable complexes with ligands – the coordinate bond is essentially a Lewis acid–base interaction, with the ligand acting as as a lewis base and the metal ion acting as a lewis acid.

Summary