---
title: "Define ligand with example"
subject: "Engineering Chemistry"
chapter: 6
key: "semester_2/engineering_chemistry:define-ligand"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/define-ligand
site: BCT Engineering
---

# Define ligand with example

Engineering Chemistry · Chapter 6: Coordination Complexes

- Asked in: 2069 Poush
- Video: [What are Ligands?](https://www.youtube.com/watch?v=011Bj5USal8) — chemistNATE
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/define-ligand
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-6

## Question

Define the term ligand with an example.

## Short answer

A ligand is an ion or molecule that donates a lone pair of electrons to a central metal atom/ion by a coordinate bond to form a complex. For example, in [Cu(NH₃)₄]²⁺, NH₃ molecules are ligands.

## Answer

A **ligand** is an ion or molecule that has at least one lone pair of electrons and donates it to a central metal atom/ion by a coordinate bond to form a complex.

Ligands may be neutral (NH₃, H₂O, CO), anionic (Cl⁻, CN⁻, OH⁻) or rarely cationic (NO⁺). They are classified as monodentate (NH₃), bidentate (en, oxalate) and polydentate (EDTA).

Example: in [Cu(NH₃)₄]²⁺, the four NH₃ molecules are the ligands donating lone pairs to Cu²⁺.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What defines a ligand?
   A. A metal ion that accepts electrons
   B. Any species with an unpaired electron
   C. An ion or molecule with at least one lone pair that donates it to the central metal by a coordinate bond
   D. An ion that forms an ionic bond with the metal
   Answer: C. Ligands are donors of lone pairs to the central metal atom/ion. (Key point: Definition of ligand)

2. Which is a bidentate ligand?
   A. Ethylenediamine (en)
   B. NH3
   C. EDTA
   D. Cl-
   Answer: A. en has two donor atoms; NH3 and Cl- are monodentate and EDTA is polydentate. (Key point: Denticity)

3. In [Cu(NH3)4]2+, what are the ligands?
   A. Cu2+
   B. The whole complex ion
   C. The 2+ charge
   D. The four NH3 molecules
   Answer: D. NH3 donates lone pairs to Cu2+, the central ion. (Key point: Ligand example)

4. Which of these is a neutral ligand?
   A. CN-
   B. CO
   C. Cl-
   D. OH-
   Answer: B. CO, NH3 and H2O are neutral; Cl-, CN- and OH- are anionic. (Key point: Types of ligand charge)