Objectives (5 - 10 minutes)

1. Understanding of atomic models: Students should be able to identify and describe the main atomic models that have emerged throughout history, from Dalton's model to the current model, the quantum model. They should understand how each model contributed to the evolution of the understanding of atoms.

2. Differentiation between models: Students should be able to compare and contrast the different atomic models, identifying the main changes and improvements that each new model brought in relation to the previous model. This includes understanding how each model explained and predicted chemical phenomena.

3. Application of knowledge: Students should be able to apply the knowledge acquired about atomic models to solve simple problems, such as determining the number of protons, electrons, and neutrons in an atom, or identifying the atomic model that best describes a specific phenomenon.

Secondary objectives:

• Development of critical thinking: By discussing the evolution of atomic models, students will be encouraged to think critically about how science evolves over time and how new discoveries can lead to a better understanding of the world around us.

• Stimulation of scientific curiosity: The discussion about atomic models, especially the quantum model, can arouse students' curiosity about quantum physics and other areas of science that are based on this model.

Introduction (10 - 15 minutes)

1. Review of previous content: The teacher should start the lesson by reviewing the basic concepts of atomic structure, such as the idea of atoms as the basic units of matter, composed of protons, electrons, and neutrons. This can be done through a quick review or a recap quiz to assess the students' level of understanding. (3 - 5 minutes)

2. Problem situation: The teacher can introduce the lesson with two problem situations that arouse students' curiosity and lead them to question the structure of atoms. For example:

   • "Imagine you are looking at a cup of coffee. How do you think the color, flavor, and temperature of the coffee can be explained in terms of atoms and their subatomic particles?"

   • "Why are some elements more reactive than others? How can the structure of atoms help us understand this?" (3 - 5 minutes)

3. Contextualization: The teacher can then contextualize the importance of studying atoms and their models by mentioning how understanding atomic structure and its evolution over time were fundamental for the development of various technologies, such as nuclear energy, semiconductors, nuclear medicine, etc. (2 - 3 minutes)

4. Introduction to the topic: To capture students' attention, the teacher can share two curiosities related to the topic:

   • "Did you know that the word 'atom' comes from Greek and means 'indivisible'? This is because, for a long time, it was believed that atoms were the smallest particles of matter and could not be divided."

   • "Einstein once said: 'Everything that is physical is made of atoms.' This statement highlights the importance of atoms for our understanding of the physical and chemical world around us." (2 - 3 minutes)

Development (20 - 25 minutes)

1. Dalton's Atomic Model (5 - 7 minutes): The teacher should start the discussion on the evolution of atomic models with Dalton's model. At this stage, the teacher should focus on the following points:

   • Dalton proposed that atoms were indivisible spheres and that all atoms of an element were identical in mass and chemical properties, while atoms of different elements were different.

   • The teacher should explain that although Dalton's model was a milestone in the history of chemistry, today we know that atoms are divisible and not all identical, as they have different numbers of protons, electrons, and neutrons.

2. Thomson's Atomic Model (5 - 7 minutes): The teacher should then move on to Thomson's model, which introduced the idea that atoms were not indivisible and contained subatomic particles called electrons. At this stage, the teacher should address:

   • The discovery of electrons through the "Thomson's Plum Pudding" experiment.

   • The fact that, in this model, electrons were uniformly spread within a sphere of positive charge, giving the atom a structure similar to a plum pudding.

3. Rutherford's Atomic Model (5 - 7 minutes): Next, the teacher should discuss Rutherford's model and the discovery of the atomic nucleus. At this stage, the teacher should emphasize:

   • The alpha particle scattering experiment, which led to the discovery that most of the atom's mass and all its positive charges are concentrated in a small, dense nucleus.

   • The idea that electrons orbit around the nucleus, similar to the movement of planets around the sun.

4. Bohr's Atomic Model (5 - 7 minutes): Finally, the teacher should address Bohr's model, which improved Rutherford's model by proposing that electrons move in circular orbits around the nucleus in fixed energy levels. At this stage, the teacher should highlight:

   • The idea that electrons can jump from one orbit to another, emitting or absorbing energy in the form of photons.

   • The explanation that the energy of electrons is quantized, meaning they can only exist at specific energy levels, not anywhere in between.

During each explanation, the teacher should encourage students to ask questions, share their own understandings, and relate the models to the problem situations presented in the Introduction.

Return (10 - 15 minutes)

1. Synthesis and Discussion (5 - 7 minutes): The teacher should review the main concepts covered during the lesson, synthesizing the atomic models presented. The goal is for students to recognize the evolution of the models and the incorporation of new discoveries and theories at each stage. The teacher can ask students what they found most interesting or surprising about each model and how they believe these discoveries impacted the worldview at the time. Additionally, the teacher can encourage students to make connections between the atomic models and the problem situations presented in the Introduction, reinforcing the applicability of these concepts.

2. Connection to the Real World (3 - 5 minutes): The teacher should then propose a discussion on the relevance of atomic models to the real world. He can ask questions such as:

   • "How can understanding atomic models help us understand everyday phenomena, such as the reaction of medications in our body, the color and luminosity of an object, the explosion of an atomic bomb, among others?"

   • "How does the evolution of atomic models reflect the evolution of science and human knowledge?"

   The goal is for students to realize that science is not a set of static facts, but a continuous process of discovery and reassessment, and that understanding atomic models is fundamental to understanding many aspects of the world around us.

3. Individual Reflection (2 - 3 minutes): Finally, the teacher should suggest that students reflect individually on what they learned in the lesson. He can ask questions like:

   • "What was the most important concept you learned today?"

   • "What questions have not been answered yet?"

   This individual reflection allows students to consolidate what they have learned and identify any gaps in their understanding that may need further clarification. Additionally, by asking for feedback on what was learned, the teacher can assess the effectiveness of the lesson and plan future activities to address any areas of difficulty or confusion identified.

Conclusion (5 - 7 minutes)

1. Summary and Recapitulation (2 - 3 minutes): The teacher should start the Conclusion by summarizing the main points covered during the lesson. He should review the different atomic models presented, from Dalton's model to Bohr's model, emphasizing the contributions of each model to the evolution of the understanding of atoms. Additionally, the teacher should highlight how the discoveries and theories of each model were incorporated into subsequent models, leading to an increasingly complex and accurate view of atomic structure.

2. Theory-Practice Connection (1 - 2 minutes): Next, the teacher should highlight how the lesson connected theory (atomic models) to practice (the application of models to solve problems and understand phenomena). He can recall the problem situations presented in the Introduction and how the atomic models helped to understand and explain these situations. Additionally, the teacher can mention other real-world examples discussed during the lesson and how atomic models help understand these examples.

3. Additional Materials (1 - 2 minutes): The teacher should then suggest some supplementary reading materials, videos, or extra activities for students who wish to deepen their understanding of atomic models. The materials may include documentaries on the history of chemistry, interactive websites that explore atomic structure in detail, or practical activities, such as building atomic models with toy parts. The teacher should encourage students to explore these materials on their own and to bring any questions or discoveries to the next lesson.

4. Importance of the Subject (1 minute): Finally, the teacher should summarize the importance of the topic covered for everyday life, highlighting how understanding atomic models is fundamental for chemistry and many other fields of science and technology. He can mention examples of how atomic models are used in practical applications, such as designing new materials, understanding biological processes, or the development of technologies like nuclear energy. Additionally, the teacher can emphasize how the discussion on the evolution of atomic models helps develop skills such as critical thinking, problem-solving, and understanding the nature of science.