Objectives (5-7 minutes)

1. Introduce students to the Bohr atomic model, explaining its importance in understanding the structure of atoms and their interactions.

2. Develop students' ability to calculate the radius and the energy of an electron in a particular energy level using the Bohr equation.

3. Apply Bohr's model to explain phenomena such as the emission and absorption of light, the formation of spectra, and the stability of atoms.

Secondary Objectives:

• To stimulate students' curiosity about Modern Physics, presenting it as a science that is constantly evolving and offering new perspectives on the world around us.

• Develop students' critical thinking skills by encouraging them to question and explore beyond the content presented, seeking to understand how scientific theories are developed and modified over time.

• Promote active learning and teamwork, through the practice of hands-on activities and group discussions.

In this stage, the teacher should clearly explain the Objectives of the class to ensure that students understand what will be addressed and what is expected of them by the end of the class.

Introduction (10-15 minutes)

1. Review of Previous Content: The teacher begins the class by briefly reviewing the concepts of atom, electron, proton, and neutron. He can do this through a quick question and answer, or ask students to recall these concepts. This review is important to ensure that all students have the necessary background to understand Bohr's model.

2. Problem Situations: The teacher can propose two situations that arouse the students' interest:

   a) "Why don't electrons fall into the atom's nucleus? If they are negatively charged and the nucleus is composed of positively charged protons, shouldn't there be an attraction pulling them to the nucleus?"

   b) "How can we explain the formation of spectral lines in the light emitted by a gas lamp? And why are these lines unique to each chemical element?"

3. Contextualization: The teacher can then explain that Bohr's model, which will be the focus of the class, was developed to answer these questions and others related to the structure of atoms. He can also mention that this model was a landmark in Physics, as it was the first to consider that electrons orbit the nucleus in well-defined layers.

4. Getting Students' Attention: To arouse students' interest, the teacher can share curiosities such as:

   a) "Did you know that the Bohr model was one of the first atomic models to be widely accepted, but today we know that it is a simplification of reality? Modern Physics, which we will study in this class, has brought new perspectives on the structure of atoms."

   b) "Bohr's studies on light emitted by atoms led to the development of spectroscopy, an important tool used in various fields, such as astrophysics, chemistry, and medicine."

5. Expectations of the Class: At the end of the Introduction, the teacher should make it clear what is expected of the students at the end of the class. He can reinforce the Objectives of the class, mention that students will have the opportunity to perform calculations and solve problems using Bohr's model, and that they will also explore applications of this model in explaining real-world phenomena.

Development (20-25 minutes)

1. Hands-on Activity - Building a Bohr's Atom Model:

   • Preparation: The teacher should divide the class into groups of 4 or 5 students and provide each group with materials such as: cardboard, colored markers, rubber bands and Styrofoam balls of different sizes (representing the protons, neutrons, and electrons, respectively). They should also provide a table with the atomic and mass numbers of some chemical elements.

   • Execution: Each group must choose a chemical element from the table, check the number of protons and neutrons in the table, and then build a Bohr atom model of that element. Electrons (smaller Styrofoam balls) should be represented in layers (rubber bands) corresponding to Bohr's energy levels, according to the formula: 2n² (where n is the energy level number). Students should color the electrons according to the spectral line rule (each color represents a specific transition between energy levels).

   • Discussion: The teacher should encourage students to discuss what they observed during the activity, how electrons are distributed around the nucleus, what happens when they gain or lose energy, and how this relates to the emission and absorption of light.

2. Problem-Solving Activity - Calculations with the Bohr Equation:

   • Preparation: The teacher should provide each group with a series of problems involving Bohr's equation. The problems should involve calculating the radius of an electron in a particular energy level, or the energy of an electron in a particular level.

   • Execution: Students, in their respective groups, should work together to solve the problems. They can use simple calculators to perform the calculations.

   • Discussion: After solving the problems, the teacher should call attention to the results obtained, explaining how they relate to Bohr's model and the phenomena of emission and absorption of light.

3. Discussion Activity - Applications of Bohr's Model:

   • Preparation: The teacher should prepare a list of questions for discussion, which may include: "How does Bohr's model help us to understand the formation of spectral lines?"; "How does Bohr's model explain the stability of atoms?"; "How does Bohr's model relate to the idea that electrons have both particle and wave characteristics?".

   • Execution: The teacher should present the questions and encourage students to actively participate in the discussion, sharing their opinions and ideas, and making connections with what they have learned throughout the class.

   • Discussion: The teacher should moderate the discussion, clarifying doubts, reinforcing important concepts, and highlighting students' contributions.

By the end of the Development, students should have a solid understanding of Bohr's model and how to use it to calculate electron properties. They should also be able to apply this model to explain phenomena such as the emission and absorption of light and the stability of atoms. In addition, through hands-on activities and discussion, they will have the opportunity to develop their critical thinking, problem-solving, and teamwork skills.

Feedback (8-10 minutes)

1. Group Discussion (3-4 minutes): The teacher should gather all the students and promote a group discussion. Each group should share their conclusions and solutions found during the hands-on and problem-solving activities. The teacher should encourage students to explain the process they used to reach their conclusions, and to express their opinions and doubts. This is a great opportunity for students to learn from each other, and for the teacher to identify gaps in students' understanding that need to be addressed.

2. Connection to Theory (2-3 minutes): After the group discussion, the teacher should make the connection between the hands-on activities and the theory presented at the beginning of the class. He should explain how Bohr's model, which was used by students to build their atom models and solve the problems, applies to the structure of atoms and the phenomena of emission and absorption of light. The teacher can use the models built by the students to illustrate these explanations.

3. Individual Reflection (1-2 minutes): The teacher should propose that students reflect individually on what they learned during the class. He can do this through questions such as: "What was the most important concept you learned today?" and "What questions have not yet been answered?". This reflection is important for students to consolidate what they have learned and identify any doubts or concepts that they have not yet fully understood.

4. Student Feedback (1-2 minutes): Finally, the teacher should ask students to provide feedback on the class. They can be asked about what they liked most about the class, what they found most challenging, and what they would like to learn more about. Student feedback is a valuable tool for the teacher to evaluate the effectiveness of their teaching strategies and make adjustments, if necessary.

By the end of the Feedback, students should have a solid understanding of Bohr's model and how to use it to calculate electron properties. They should also be able to apply this model to explain phenomena such as the emission and absorption of light and the stability of atoms. In addition, through hands-on activities, discussion, and reflection, they will have had the opportunity to develop their critical thinking, problem-solving, and teamwork skills. Student feedback will help the teacher to assess the success of the class and plan future learning activities.

Conclusion (5-7 minutes)

1. Summary of Content (2-3 minutes): The teacher should summarize the main points covered during the class, reinforcing Bohr's atomic model, the distribution of electrons in layers, and the calculation of the radius and energy of an electron in a particular energy level. He can make a brief review of Bohr's equation and the spectral line rule. This recap is important to consolidate student learning and ensure they have understood the fundamental concepts.

2. Connection of Theory with Practice (1-2 minutes): The teacher should explain how the hands-on activities carried out by the students relate to the theory presented. He can highlight how building the Bohr atom model and solving problems with Bohr's equation help visualize and apply the theoretical concepts. The teacher can also mention how the group discussion and individual reflection allowed students to deepen their understanding and develop their critical thinking skills.

3. Complementary Materials (1-2 minutes): The teacher should suggest additional materials for students who wish to further their studies on the Bohr model. These materials may include textbooks, scientific journal articles, online educational videos, and interactive simulations. The teacher can also recommend extra exercises for students to practice using Bohr's equation. The goal is to provide students with resources that they can use to review the class content and expand their knowledge on the subject.

4. Relevance of the Subject (1 minute): To conclude the class, the teacher should emphasize the importance of Bohr's model and Modern Physics in our daily lives. He can mention how the understanding of the structure of atoms and the phenomena of emission and absorption of light has practical applications in areas such as Chemistry, Physics, Engineering, and Medicine. The teacher can also emphasize that the study of Modern Physics is not restricted to classrooms and laboratories, but is present in various aspects of our daily lives, from the technology we use to the stars we observe in the sky.