Developing understanding of covalent bonding

This worksheet is 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. 

Learning objectives

1. Recognise a diagram that shows the structure of a given covalent compound.
2. Draw and connect a dot and cross diagram with a molecule diagram.
3. Use dot and cross diagrams to explain the construction of molecular models.
4. Draw dot and cross diagrams and 3D models from the formula of a given covalent compound.
5. Explain why silicon dioxide forms a giant covalent structure.

How to use this resource

This resource aims to develop learners’ understanding of covalent structures. The questions encourage learners to visualise covalent molecules in different ways and think about how this relates to the sub-microscopic level. As a result, learners should develop more secure mental models to support their thinking about this topic. 

• When to use? Use after initial teaching or discussion of this topic to develop ideas further. You can also use as a revision activity.
• Group size? Suitable for independent work either in class or at home. Or use the questions for group or class discussions.
• How long? 15–30 mins

Johnstone’s triangle

Johnstone’s triangle is a model of the three different conceptual levels in chemistry: macroscopic, symbolic and sub-microscopic. You can use Johnstone’s triangle to build a secure understanding of chemical ideas for your learners.

Introduce learners to Johnstone’s triangle with our Covalent bonding Johnstone’s triangle worksheet which encourages learners to represent and explain the properties of water using their sub-microscopic understanding of covalent bonding.

Johnstone’s triangle and this resource

The icons in the margin indicate which level of understanding each question is developing to help prompt learners in their thinking.

• Macroscopic: what we can see. Think about the properties that we can observe, measure and record.
• Sub-microscopic: smaller than we can see. Think about the particle or atomic level.
• Symbolic: representations. Think about how we represent chemical ideas including symbols and diagrams.

The levels are interrelated, for example, learners need visual representation of the sub-microscopic in order to develop mental models of the particle or atomic level. Our approach has been to apply icons to questions based on what the learners should be thinking about.

Questions may be marked with two or all three icons, indicating that learners will be thinking at more than one level. However, individual parts of the question may require learners to think about only one or two specific levels at a time.

Support

This worksheet is ramped so that the earlier questions are more accessible. The activity becomes more challenging in the later questions. You can give extra explanations for the more challenging questions. If completing as an in-class activity it is best to pause and check understanding at intervals, as often one question builds on the previous one.

It is useful for learners to observe macroscopic properties first-hand. You could circulate examples of substances in the classroom, run a class practical of a chemical reaction or show a teacher demonstration of properties.

Give learners physical models to use and manipulate, such as a Molymod™ kits or counters.

Additional support may be needed for any learners still lacking in confidence in the required symbolic representation, for example by sharing and explaining a diagram or a simulation that can show movement of the particles.

Answers and guidance

Download the teacher notes to find the answers to the student worksheet.

There are six multi-part questions in the student worksheet. Question 1 assumes that learners are already familiar with basic particle diagrams and the reason for using different colours. They are then asked to connect these familiar particle representations with the displayed formula in question 2.

Questions 3, 4 and 5 introduce dot and cross diagrams as another representation. Question 3 supports learners to explain the number of bonds a carbon or hydrogen atom can make in a displayed formula diagram, using dot and cross diagrams. This illustrates how different symbolic representations can help understanding in different ways. Question 4 uses learners’ dot and cross diagrams to explain the construction of Molymod™ components by recognising that the number of holes matches the number of bonds each type of atom can form. The question also supports learners to compare a 2D displayed formula with a 3D physical model. Question 5 continues this by supporting learners to connect 2D dot and cross diagrams with the 3D shape of a molecule.

The final question challenges learners to use different representations of silicon dioxide to explain why it forms a giant structure.