Chapter 11 : Chemical Bonding

Properties of Ionic Compounds (giving)

1. High Melting and Boling Point

   • They have giant ionic lattice structures, a large amount of energy is needed to overcome the strong electrostatic forces of attraction between the oppositely charged ions

2. Conducts Electricity in Molten and Aqueous States but not in Solid State

   • The ions are held in fixed positions in a giant ionic lattice structure by strong electrostatic forces of attraction

   • The ions are unable to move freely to conduct electricity thus there are no mobile charged carriers

3. Hard but brittle

   • A large amount of energy is needed to overcome the strong electrostatic forces of attraction between the cation and the anions

   • When a large enough force is applied, the layer of ions can slide bringing ions of like charges next to each other. These ions of like charges repel each other and the ionic lattice shatters

4. Generally soluble in water and insoluble in organic solvents

Covalent Bonding (sharing) - Simple Molecular Structure

1. Low Melting and Boiling Points

   • They have a simple molecular structure. Little energy is required to overcome the weak intermolecular forces of attraction

2. Does not conduct electricity

   • Due to the absence of mobile ions

3. Soluble in organic solvents but insoluble in water

Macromolecules (Polymers)

1. No fixed melting or boiling point

2. Does not conduct electricity in any state

3. Most are soluble in organic solvents but insoluble in water

4. Vary greatly in hardness and flexibility

Giant Covalent Structure - Diamond

1. Structure

   • Carbon atom is bonded to 4 other carbon atoms by strong covalent bonds

2. High Melting and Boiling point

   • They have a giant molecular structure and a large amount of energy is needed to break the strong covalent bonds between the atoms

3. Hard

   • It has a giant molecular structure all the atoms are held together by strong covalent bonds which require a large amount of energy to break

4. Does not conduct electricity

   • All valence electrons of carbon are used for bonding so there are no mobile electrons

Giant Covalent Structure - Graphite

1. Structure

   • Each carbon atom is bonded to 3 other carbon atoms

   • Has a layered structure in which weak molecular forces hold the layers together

2. High melting and boiling points

3. Soft and slippery

   • Layers of carbon can easily slide over one another since the weak intermolecular forces of attraction joining the layers an be overcome by a small amount of energy supplied

4. Good conductor of electricity (conducts along the layers

   • Each carbon atom can only make use of 3 valence electrons not used in bonding the electrons not used in bonding are mobile and can conduct electricity

Giant Covalent Structure - Silicon dioxide

1. Structure

   • Each silicon atom is bonded to 4 oxygen atoms and each oxygen atom is bonded 2 silicon atoms by strong covalent bonds

2. High melting and boiling points

3. Hard

   • Silicon dioxide has a giant molecular structure. All the atoms are held together by strong covalent bonds which require a large amount of energy to break.

4. Does not conduct electricity

Metallic bonding

1. Structure

   • Giant metallic lattice structure

   • Strong electrostatic forces of attraction between positive ions and sea of delocalized electrons

2. High melting and boiling point

3. Good conductor of electricity

   • Presence of delocalized electrons which can move freely through the giant metallic lattice structure

4. Malleable and ductile

   • pure metal atoms of the same size are arranged in a regular orderly manner, allowing the layers of atoms to slide over one another easily when a force is applied

5. Good thermal conductivity

   • When the temperature at one end of a metal is increased, the mobile electrons at the heated end gain energy and move more rapidly

   • they collide rapidly transferring energy from one electron to another

6. Solubility in Water and Organic Solvents

Alloys

1. Definition

   • A mixture of metal with one or more other elements

2. Properties

   • Stronger and harder

     • The size of the atoms of the added element is different from that of the atoms of the parent element

     • This disrupts the regular, orderly arrangement of the metal ions making it more difficult for the layer of atoms to slide over one another

   • Does not conduct electricity and thermal energy as well

     • the conduction of alloy is poorer compared to a pure metal as the movement of electrons is hindered due to irregular arrangements of atoms