What is a coordinate covalent bond, and how does it differ from a covalent bond?
Ch.4 Molecular Compounds
Chapter 4, Problem 38
Which of the following contains a coordinate covalent bond? (Hint: How many covalent bonds would you expect the central atom (underlined/bold) to form?)
a. PbCl2
b. Cu(NH3)42+
c. NH4+
Verified step by step guidance1
Identify the definition of a coordinate covalent bond: A coordinate covalent bond occurs when one atom donates both electrons to form a shared pair in a covalent bond, typically seen in complex ions or molecules.
Analyze option a (PbCl₂): Lead (Pb) forms bonds with chlorine (Cl) through regular covalent or ionic bonding. There is no evidence of a coordinate covalent bond here.
Analyze option b (Cu(NH₃)₄²⁺): In this complex ion, the central copper ion (Cu²⁺) is surrounded by four ammonia (NH₃) molecules. Each NH₃ molecule donates a lone pair of electrons to the Cu²⁺ ion, forming coordinate covalent bonds.
Analyze option c (NH₄⁺): The ammonium ion (NH₄⁺) is formed when an NH₃ molecule donates a lone pair of electrons to a hydrogen ion (H⁺). This results in a coordinate covalent bond between NH₃ and H⁺.
Conclude: Based on the analysis, options b (Cu(NH₃)₄²⁺) and c (NH₄⁺) contain coordinate covalent bonds, while option a (PbCl₂) does not.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Covalent Bonding
Covalent bonding occurs when two atoms share one or more pairs of electrons, allowing each atom to attain a stable electron configuration. This type of bond is typically formed between nonmetals and can be classified into single, double, or triple bonds based on the number of shared electron pairs.
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Coordinate Covalent Bond
A coordinate covalent bond, also known as a dative bond, is a specific type of covalent bond where one atom donates both electrons to the bond. This often occurs in complex ions or molecules where a central atom, such as a metal, accepts a lone pair of electrons from a donor atom, leading to unique bonding scenarios.
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Central Atom and Valency
The central atom in a molecule is typically the atom that forms the most bonds and is often a metal or a nonmetal with a higher valency. Understanding the expected number of bonds that the central atom can form is crucial for predicting the type of bonds present, including whether coordinate covalent bonds are involved in the structure.
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