Intermediate Topic 204 of 1102 Bonding & Molecular Structure
Ligands
Ions or molecules that donate electron pairs to a central metal ion.
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In-depth explanation of Ligands
A ligand is an ion or molecule that donates one or more electron pairs to a central metal ion, acting as a Lewis base. Ligands are classified by the number of donor atoms they use: monodentate ligands bind through one atom, while polydentate ligands bind through two or more. Common monodentate ligands include water, ammonia, chloride and cyanide, and carbon monoxide binds through its carbon atom. Ethylenediamine and EDTA are polydentate examples. The identity of the ligand strongly influences the colour, stability and reactivity of the complex.
Going deeper: Ligands
Key ideas: Know the common ones with charge and name: H2O aqua, NH3 ammine, Cl- chlorido, CN- cyanido, OH- hydroxido, CO carbonyl, NO2- nitrito-N or nitrito-O, en (neutral, bidentate), ox 2- (bidentate), EDTA 4- (hexadentate). Ambidentate ligands such as SCN- can bind through S or N. Spectrochemical order predicts the field strength.
Common mistakes and connections: Mistakes include treating ligand charge incorrectly when finding oxidation state (NH3 and H2O are neutral), mixing up ambidentate with polydentate, and writing the wrong donor atom for CO (C), or NO2 (N or O). Links to Lewis bases, chelation, linkage isomerism and crystal field strength.
Visualization of Ligands
Denticity counts how many donor atoms a ligand uses: water and ammonia are monodentate, ethylenediamine bidentate, and EDTA hexadentate. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Ethylenediamine binds to a metal through its two nitrogen atoms, forming a five-membered chelate ring.
Frequently asked questions about Ligands
What is Ligands?
Ions or molecules that donate electron pairs to a central metal ion.
Is Ligands a beginner, intermediate or advanced topic?
Ligands is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
What should I learn before Ligands?
Study these earlier topics in Bonding & Molecular Structure first: Graphene, Fullerenes, Coordination Compounds.
What comes after Ligands?
The next topics in Bonding & Molecular Structure are Coordination Number and Chelation.
Can I practise Ligands with quizzes?
Yes. The interactive lesson includes a self-check question on Ligands, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where Ligands fits in Bonding & Molecular Structure
Ligands is topic 89 of 104 in Bonding & Molecular Structure.