Covalent and Coordinate Bonding

This page delves into covalent bonding and coordinate (dative covalent) bonding for AQA A Level Chemistry.

Covalent bonding is defined as a pair of electrons shared between two atoms. The strength of covalent bonds is generally high, with smaller atoms forming stronger bonds due to closer proximity of electrons to nuclei.

Coordinate bonding is introduced as a special type of covalent bond where both electrons come from the same species. The page explains when coordinate bonds are possible and provides an example with H₂O and H⁺.

Vocabulary: Coordinate (dative covalent) bonding is a type of covalent bond where both electrons are donated by one atom.

The page also covers giant covalent structures, which form when bonds between atoms continue indefinitely to create a giant lattice.

Example: Diamond and graphite are examples of giant covalent structures with very different properties due to their structural differences.

Properties of giant covalent structures are discussed:

1. High melting and boiling points
2. Variable electrical conductivity
3. Hardness and brittleness

Highlight: The properties of giant covalent structures are directly related to their bonding and structural arrangements.

Bonding and Physical Properties

This final page summarizes the relationship between bonding and physical properties for AQA A Level Chemistry, tying together concepts from ionic, covalent, and metallic bonding.

The page presents a comparative overview of different types of structures and their properties:

1. Ionic compounds:

   • High melting and boiling points
   • Brittle when solid
   • Conduct electricity when molten or dissolved

2. Simple molecular structures:

   • Low melting and boiling points
   • Soft or gaseous at room temperature
   • Poor electrical conductors

3. Giant covalent structures:

   • Very high melting and boiling points
   • Hard and strong
   • Variable electrical conductivity (e.g., diamond vs. graphite)

4. Metallic structures:

   • Variable melting and boiling points
   • Malleable and ductile
   • Good electrical conductors

Highlight: Understanding the relationship between bonding type, structure, and physical properties is crucial for predicting and explaining the behavior of different substances.

The page emphasizes the importance of considering both the type of bonding within a substance and the forces between particles when explaining physical properties.

Example: The high melting point of sodium chloride (NaCl) can be explained by the strong ionic bonds in its giant ionic lattice, while the low melting point of iodine (I₂) is due to weak van der Waals forces between simple molecules.

The concept of structure-property relationships is reinforced, encouraging students to apply their knowledge of bonding to explain and predict the properties of various substances.

Vocabulary: Structure-property relationships refer to the way in which the microscopic structure and bonding of a substance determine its macroscopic physical and chemical properties.