Lesson Plan | Traditional Methodology | Atoms: Energy Levels and Sublevels

Objectives

Duration: (10 - 15 minutes)

The purpose of this stage is to establish a clear and precise understanding of the main objectives of the lesson, allowing students to know exactly what is expected of them. This helps to direct their attention to the key points of the content and ensures that the teacher can focus on the most important areas during the explanation. A well-defined start creates a solid foundation for the entire development of the lesson.

Main Objectives

1. Understand that electrons are arranged in energy levels and sublevels.

2. Comprehend the reason for this distribution.

3. Find the energy of a particular electron.

Introduction

Duration: (10 - 15 minutes)

The purpose of this stage is to capture the students' attention and prepare them for the more technical content that will be addressed next. By providing an initial context and interesting curiosities, students can feel more engaged and motivated to understand the importance of the topic that will be covered in the lesson.

Context

Start the class by explaining that matter is made up of atoms, which in turn are formed by a nucleus and an electron cloud. Emphasize that the electron cloud is where the electrons are located and that these electrons are not arranged randomly, but rather organized into energy levels and sublevels. Use a simple analogy, like the structure of a building, where each floor represents an energy level and the apartments within each floor represent the sublevels.

Curiosities

Did you know that the distribution of electrons in energy levels and sublevels is fundamental to the functioning of everything around us? For example, the color of a firework is determined by electrons jumping between different energy levels in the atoms of chemical elements. This phenomenon is utilized in various areas of technology and science, such as in the creation of lasers and material analysis.

Development

Duration: (40 - 50 minutes)

The purpose of this stage is to provide a detailed and systematic understanding of electron distribution in atoms, clarifying how energy levels and sublevels are organized and how this affects the properties of elements. This section is crucial for consolidating theoretical knowledge and enabling students to apply this information in calculations and practical representations.

Covered Topics

1. Energy Levels: Explain that electrons are distributed in different energy levels around the nucleus of the atom. Each energy level is represented by a principal quantum number (n), which can be a positive integer. The larger the value of n, the higher the energy and distance of the electron from the nucleus. 2. Energy Sublevels: Detail that each energy level is subdivided into sublevels, designated by the letters s, p, d, and f. Each sublevel has a specific shape of orbital and a defined number of electrons it can accommodate: sublevel s can have up to 2 electrons, p up to 6, d up to 10, and f up to 14. 3. Electronic Distribution: Describe how electrons are distributed in the energy levels and sublevels following the Aufbau Principle, Hund's Rule, and the Pauli Exclusion Principle. Explain that electrons fill the lowest energy orbitals first and that each orbital can accommodate a maximum of two electrons with opposite spins. 4. Electron Energy: Explain how the energy of an electron is determined by its energy level and sublevel. Use the formula E_n = -13.6 eV/n² to calculate the energy of electrons in a hydrogen atom, where E_n is the energy at level n. Emphasize that this formula is specific to hydrogen and that for other elements, the energy depends on more complex interactions.

Classroom Questions

1. Calculate the energy of an electron at the energy level n=3 in a hydrogen atom. 2. Explain why electrons fill the 4s sublevel before the 3d. 3. Draw the electronic distribution of the element oxygen (Z=8), indicating the filled energy levels and sublevels.

Questions Discussion

Duration: (20 - 25 minutes)

The purpose of this stage is to consolidate the knowledge acquired by the students throughout the lesson, providing a space to discuss and clarify doubts. Through a detailed discussion of the questions and engaging students with reflective questions, it is possible to ensure that the concepts have been fully understood and that the students are capable of applying this knowledge in varied contexts.

Discussion

• Calculate the energy of an electron at the energy level n=3 in a hydrogen atom: Explain that the formula for calculating the energy of an electron in a hydrogen atom is E_n = -13.6 eV/n². By substituting n with 3, we get E_3 = -13.6 eV / 3² = -13.6 eV / 9 ≈ -1.51 eV. Therefore, the energy of an electron at level n=3 in a hydrogen atom is approximately -1.51 eV.

• Explain why electrons fill the 4s sublevel before the 3d: Detail that the order of electron filling in sublevels follows the Aufbau Principle, which states that orbitals are filled in order of increasing energy. Although 4s numerically comes after 3d, the 4s sublevel has a slightly lower energy than 3d, which is why it is filled first.

• Draw the electronic distribution of the element oxygen (Z=8), indicating the filled energy levels and sublevels: Describe that the electronic distribution of oxygen is 1s² 2s² 2p⁴. This means the first two electrons are in the 1s level, the next two electrons are in the 2s level, and the remaining four electrons are in the 2p sublevel. To draw, show that at level 1 we have one s orbital with 2 electrons, and at level 2 we have one s orbital with 2 electrons and one p orbital with 4 electrons.

Student Engagement

1. How does the distribution of electrons in energy levels and sublevels influence the chemical properties of elements? 2. Why is it important to understand electronic distribution for the comprehension of the periodic table? 3. What are the implications of electronic distribution in the formation of chemical bonds? 4. How can the energy of electrons in different levels and sublevels affect the reactivity of an element? 5. Discuss how electronic distribution can be used to explain phenomena observed in everyday life, such as the color of a firework flame.

Conclusion

Duration: (10 - 15 minutes)

The purpose of this stage is to provide a clear and organized closure for the lesson, recapping the main points discussed and reinforcing the importance of the content. This helps consolidate the knowledge acquired by the students, ensuring that they leave the lesson with a solid understanding and a clear vision of how to apply these concepts in different contexts.

Summary

• Electrons are distributed in energy levels around the nucleus of the atom.
• Each energy level is subdivided into sublevels designated by the letters s, p, d, and f.
• Electronic distribution follows the Aufbau Principle, Hund's Rule, and the Pauli Exclusion Principle.
• The energy of electrons can be calculated using the formula E_n = -13.6 eV/n² for hydrogen atoms.
• The order of filling energy sublevels determines the chemical properties of elements.

During the lesson, the theory about energy levels and sublevels was connected with practice through detailed examples and specific calculations. Electronic distribution was illustrated with practical examples, such as the configuration of oxygen, allowing students to visualize how these theoretical concepts are applied in practice. Additionally, the energy of electrons was calculated, demonstrating the direct application of the formulas presented.

Understanding electronic distribution is fundamental for various aspects of everyday life and science, such as explaining colors in fireworks and creating advanced technologies like lasers. This understanding is also essential for material analysis and predicting the chemical properties of elements, which are basic knowledge for many scientific and technological professions.