Developing understanding of atomic structure

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. Use atomic number and mass number to work out the number of different sub-atomic particles in one atom.
2. Label the different parts of an atom as represented using the atomic model.
3. Use an atomic structure diagram to interpret a metallic bonding diagram.
4. Use appropriate models of the atom to create explanations.

This resource aims to develop learners’ understanding of the structure of the atom. The questions encourage learners to think about different representations of atomic structure and what those representations mean at 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 Atomic structure of lithium Johnstone’s triangle worksheet which guides learners to think about the sub-atomic particles that make up a Lithium atom.

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

There are three multi-part questions in the student worksheet. The first question consolidates learners’ understanding of the different types of each sub-atomic particle and how the number of each can be worked out from the atomic number and mass number. Question two develops learners’ understanding of the connection between the charge of individual particles, the overall charge of the nucleus and the whole atom (sub-microscopic understanding) and the type of force between the nucleus and electrons.

Question 3 develops learners’ understanding of how helium can be represented by both the particle model and atomic model (symbolic understanding) and asks them to consider which model can best explain (sub-microscopic understanding) physical properties of helium (macroscopic understanding), encouraging students to consider the strengths of each model and the importance of using the most appropriate model to explain a given phenomenon.