Topic 4: Bonding

God Bless the Internet!

The bonding unit builds on the understanding of bonding developed at IGCSE level, to consider in great depth the actual mechanics of bonding, and how this impacts the physical properties of compounds.

Whilst the topic does cover metallic and ionic bonding, it focuses overwhelmingly on covalent bonding looking at and we will consider:

• The shapes of molecules
• The polarity of molecules
• The intermolecular forces between molecules
• The formation of sigma and pi bonds
• The effects of delocalisation of electrons.

The unit will take about 4 weeks and will be assessed by a joint test with the periodicity unit and an internal assessment.

Presentation:

You are strongly encouraged to use this in lessons, and make notes on it. Used in conjunction with the experiments it more or less contains everything you need to know:

Experiments and Worksheets:

• Intermolecular Forces
• Modelling Molecular Shapes

Around the Web:

Richard Thornley

• Well produced and clearly explained videos on every section of the topic.

chemguide

• Very nicely explained, striking a good balance between simplicity and depth. Designed for A-Level but fine for IB

PhET

• Excellent simulations of some of the core concepts:
  • Molecular Shapes
  • Molecular Polarity

Intermolecular Forces Experiment Data (Mr Newton’s Class)

This is the data from the intermolecular forces experiment:

1. Describe and explain the relationship between the size of the temperature drop and the intermolecular forces.
2. Which compounds had the highest and lowest intermolecular forces? Is this what you would expect?
3. Analyse and explain the following:

• The trend in intermolecular forces for the alcohols
• The trend in intermolecular forces for the alkanes

4. Compare and explain:

• Intermolecular forces in hexane and dichloromethane
• Intermolecular forces in butanol and pentane