Molecular Polarity

One of the key skills in this unit is to determine whether a molecule is polar or not. Once we know that, we can explain some of its physical and chemical properties.

Molecular Shapes and the VSEPR Theory

Lewis Dot Diagrams

Electronegativity - Covalent or Ionic?

In this part of the topic, we are focusing on Molecular Substances. Before we can start, we need to be able to work out if a substance is molecular or not. Molecular substances contain Covalent Bonds. How do we decide if a substance contains covalent bonds or not?

Particles Overview

We then looked at two covalent network solids with very different properties: graphite and diamond.

A model of diamond showing the 3D lattice - 4 covalent bonds per carbon atom.

A model of graphite showing 2D sheets - 3 covalent bonds per carbon
atom with valence electrons between the sheets

Our next task was to explore a couple of the characteristic physical properties of these allotropes of carbons: hardness; and electrical conductivity. The trick is to link these properties to the particles and/or bonds/forces within the substance.

Particles, Forces and Properties

We started looking at the relationship between particles, forces (bonds) and properties, using metallic and ionic solids as our context:

Particles - Introduction

In this topic, we are looking at pure substances. What are the particles that make up pure substances? What are the forces/bonds that hold them together (in the solid state)? How can I show this as a diagram?