Metallic bonding

Part of the Johnstone’s triangle series of resources, designed to help learners to move between different conceptual levels of thinking in key chemistry topics.

Johnstone’s triangle

Learning objectives

1. Describe a metal and its uses based on observations.
2. Use symbolic models to represent metallic bonding.
3. Explain how the type of bonding in a metallic compound relates to the properties you can observe.

How to use Johnstone’s triangle

Use Johnstone’s triangle to develop learners thinking about scientific concepts at three different conceptual levels:

• Macroscopic: what we can see. Think about the properties that you can observe measure and record.
• Sub-microscopic: smaller than we can see. Think about what is happening at a particle or atomic level.
• Symbolic: how we represent what is happening. Think about the models you use to represent what you cannot see, including diagrams and symbols.

For learners to gain a deeper understanding of a topic, they need to understand it at all three levels. Read more about how with these articles:

• Develop deeper understanding with models
• Improve students’ understanding with Johnstone’s triangle

This worksheet is best used as a whole-class or small-group activity before following up with the Developing understanding worksheet for individual practice.

Scaffolding

The worksheet includes scaffolding in each section to support learners as they produce their answers.

Share the structure of the triangle with learners prior to use. Also, tell them why you want them to use the triangle and how it will help them to develop their understanding.

Use an ‘I try, we try, you try’ approach when you are introducing Johnstone’s triangle for the first time, as detailed in the article Develop deeper understanding with models.

Next steps

The completed Johnstone’s triangle can be used as a support document when learners move on to complete the associated Developing understanding worksheet.

Developing understanding

Learning objectives

1. Use an appropriate model to explain the properties of a metal or alloy.
2. Explain why a positive ion is charged.
3. Use an atomic structure diagram to interpret a metallic bonding diagram.
4. Describe the nature of metallic bonding.
5. Evaluate a model of metallic bonding.

How to use Developing understanding

These questions are designed to help develop your learners’ mental models of metallic bonding and structure. The icons in the margin indicate which level/s of understanding each question is developing.

• Macroscopic: what we can see. Think about the properties that you can observe measure and record.
• Sub-microscopic: smaller than we can see. Think about what is happening at a particle or atomic level.
• Symbolic: how we represent what is happening. Think about the models you use to represent what you cannot see, including diagrams and symbols.

Learners should first complete the Metallic bonding: Johnstone’s triangle worksheet and may refer to this for support as they answer these questions.

For questions with the macroscopic icon in the margin, it would be useful for learners to be able to observe these macroscopic properties first-hand. This can be done by circulating examples in the classroom or showing a teacher demonstration of properties. For questions with the symbolic icon in the margin, it would be useful to have physical models for learners to use and manipulate, such as a Molymod™ kit.

The worksheet can be used in a variety of ways. It will work best as a follow-up activity to an initial teaching or discussion of ionic bonding. This could be straight away in the same lesson or as a homework. If completing in class it would be best to pause and check understanding at intervals as some questions build on previous answers. The resource could also be used as retrieval/revision activity to check that misconceptions have not crept in.

The resource works well for independent work, but the questions could also be used for group or class discussions.

Depending on the learners, the activity should take 15–30 minutes to complete.

Scaffolding

The earlier questions are designed to be accessible to all learners, later questions become more challenging. Teachers may choose to give extra explanations for the more challenging questions.