Simple Molecules (Edexcel GCSE Chemistry)

Dot & Cross Diagrams for Molecules

• Covalent substances tend to have small molecular structures, such as H₂, H₂O or CO₂

• These small molecules are known as simple molecules

• Small covalent molecules can be represented by dot and cross diagrams

• You need to be able to describe and draw the structures of the following molecules using dot-and-cross diagrams: hydrogen (H₂), hydrogen chloride (HCl), water (H₂O), methane (CH₄), oxygen (O₂) and carbon dioxide (CO₂)

• The correct dot and cross diagrams for these molecules are shown below:

Dot & cross representation of a molecule of hydrogen

Dot & cross representation of a molecule of hydrogen chloride

Dot & cross representation of a molecule of water

Dot & cross representation of a molecule of methane

Dot & cross representation of a molecule of oxygen

Dot & cross representation of a molecule of carbon dioxide