Topic 2: Bonding

Definition of Ionic Bonding

The electrostatic attraction between oppositely charged ions.

Formation of Metal Ions

Metals lose outer shell electrons to form positive ions.

Formation of Non-metal Ions

Non-metals gain electrons into their outer shell to form negative ions.

Structure of Ionic Compounds

A giant ionic lattice with regular arrangements of ions.

Why do ionic compounds have high melting points?

Strong electrostatic forces of attraction in all directions require a lot of energy to break.

Ionic conductivity: Solid vs Molten

Solids do not conduct (ions fixed); molten/aqueous do conduct (ions free to move and carry charge).

Definition of Covalent Bonding

The sharing of pairs of electrons between non-metal atoms.

Simple Molecular substances: Bonding vs Forces

Strong covalent bonds within molecules, but weak intermolecular forces between molecules.

Why do simple molecules have low boiling points?

Little energy is needed to overcome the weak intermolecular forces (the covalent bonds do NOT break).

Boiling point trend for simple molecules

As molecules get larger, intermolecular forces increase, and boiling points rise.

Giant Covalent Structure: Diamond

Each carbon atom forms four covalent bonds in a very rigid giant lattice.

Why is Diamond hard?

It has many strong covalent bonds that require massive energy to break.

Giant Covalent Structure: Graphite

Each carbon atom forms three covalent bonds, creating layers of hexagonal rings.

Why can Graphite conduct electricity?

It has one delocalised electron per carbon atom which can move through the structure and carry charge.

Why is Graphite soft/slippery?

There are no covalent bonds between layers, only weak intermolecular forces, so layers can slide.

Graphene definition

A single layer of graphite (one atom thick) that is very strong and conducts electricity.

Fullerenes: Buckminsterfullerene

Molecules of carbon with hollow shapes (C60 is a sphere).

Carbon Nanotubes: Uses

High tensile strength and conductivity; used in nanotechnology and electronics.

Metallic Bonding description

A lattice of positive metal ions surrounded by a sea of delocalised electrons.

Why are metals good conductors?

Delocalised electrons are free to move through the whole structure and carry thermal energy and charge.

Why are pure metals malleable?

Atoms are arranged in regular layers which can slide over each other.

Alloy definition and properties

A mixture of metals; different sized atoms distort layers so they cannot slide, making it harder.

States of Matter: (s), (l), (g), (aq)

Solid, Liquid, Gas, and Aqueous (dissolved in water).

State change: Melting/Boiling

Energy is needed to overcome the forces of attraction between particles.

Size of Nanoparticles

Between 1 and 100 nanometres (nm).

Nanoparticle Surface Area to Volume Ratio

Extremely high; a small amount of material has a massive surface area.

Benefit of High SA:V in Nanoparticles

Smaller quantities are needed to be effective (e.g., in catalysts or suncreams).

Risk of Nanoparticles

They are so small they might be able to enter the skin or cells and cause unknown health damage.

Particulate matter (PM) sizes

Fine particles (PM2.5) are 100-2500nm; Coarse particles (dust) are 2500-10,000nm.

Why do giant structures have high melting points?

All atoms/ions are linked by strong bonds (covalent, ionic, or metallic) throughout the whole structure.