This unit lays the foundation for understanding the structure of atoms, particularly with regard to their subatomic particles, element identity and the organization of the periodic table. The material is presented in the context of stars, as all chemical elements are formed in stars and supernova explosions. The main activity consists of modeling atoms through alpha fusion processes, which provides a uniquely tangible understanding for the students. This lesson may be used as part of an Earth Science or introductory Chemistry class.

  • Students will know the subatomic particles (proton, neutron, electron).
  • Students will know that an atom’s identity (number) is equal to the number of protons.
  • Students will know that atomic mass is determined by the sum of the number of protons and neutrons.
  • Students will know the proton-proton chain reaction that leads to the formation of helium during hydrogen fusion in stars.
  • Students will know that the chemical elements from hydrogen to iron can be formed in stars through stellar fusion.
  • Students will be able to explain the formation of elements through the alpha ladder.
  • Students will know that the chemical elements heavier than iron are formed in supernova explosions.
  • Students will be able to explain the formation of heavier elements as a series of particle collisions and subsequent nuclear decay processes.
  • Students will be able to apply their understanding of the formation of chemical elements to explaining the organization of the periodic table.
  • Warm colors are red, orange and yellow and are therefore hotter.
  • Cool colors are green, violet and blue and therefore have lower energy.
  • The stars are smaller than the Sun.
  • The Sun is not a star.
  • Stars can fall.
  • Elements are formed under high pressure in the earth.
  • Atoms can be seen in a microscope.
  • Atoms can be divided.
  • The identity of an atom depends on what it looks like.
  • The atom is the smallest unit of matter.
  • The chemical elements simply exist, and have no specific or known origins.
  • Stars like the Sun burn forever and do not change.
  • All elements are equally abundant in the solar system.
  • The periodic table is organized in the order of the discovery of the elements.
  • All elements produced in the supernova are immediately stable.
  • This unit involves 5 brief PowerPoint lectures, 5 group-worksheets and 2 main activities that focus on proton-proton-fusion and alpha fusion. The PowerPoint lectures are to be presented interactively by the teacher, eliciting questions and answers when appropriate. The group worksheets are follow-ups to the lectures and are provided in order to reinforce student-learning and facilitate group understanding (where students help one another). The lesson centers around the two activities, where the students first model proton-proton fusion and then “build” atomic models using the concept of alpha fusion. In tandem with the periodic table, these activities will emphasize the structure and identity of the chemical elements.
  • Introduction to the Electromagnetic Spectrum, including an “ice-breaker” activity with mood beads.
  • Introduction to stellar evolution, their source of energy and the life cycle of stars.
  • A detailed look at nuclear fusion with attention to proton-proton fusion.
  • An exploration of the formation of elements (up to iron) through the process of alpha fusion.
  • A review of the processes that form the elements heavier than iron.
  • This unit was designed for use in a 9th grade Earth Science classroom in San Diego, CA. These activities took place twice a week for three weeks arid were largely integrated into the standard classroom curriculum (allowing for off-days to be taught by the teacher). The class periods were 50-minutes and the lesson was taught to five different periods. These lessons were taught in the beginning part of the year, as an introduction to chemistry, which would be used throughout the course. It may also be used in a chemistry class, either as an introduction or a review of fundamental concepts.
  • Students will be evaluated throughout the lesson mainly through their performance in the modeling of the atoms. In addition, their diagram of the life cycle of stars and associated worksheet activities (may be assigned as homework) should also be used to test for understanding.
  • As they build the atoms and grow familiar with the two subatomic particles (protons and neutrons), they will develop their understanding of the structure and identity of atoms. In particular, as these activities are done in pairs and take a substantial portion of the class-time, this allows for instructors to circulate and answer questions as they arise. The students not only discover their own difficulties and questions with the material, but are given the time to obtain answers and clarification. In this way, the students come away with a reinforced understanding of the main concept of atomic structure and the periodic table.
  • The students will produce a model of proton-proton fusion using craft supplies. In addition, each pair of students will build on an initial alpha particle in order to create a final nucleus of iron.
  • The supplies for the model-building consist of two different colors of cotton balls, with one color representing protons (e.g. white) and another for neutrons (e.g. red).
  • Using glue and a paper backing, the students should model proton-proton fusion as modeled in Lesson 3, slides 6-9.
  • In the next step, they should start with an alpha particle model and continue to add an alpha particle (2 neutrons and 2 protons) until they have a Fe-52 nucleus.
  • These lessons require interactive presentation skills and full engagement in student learning throughout the allotted activity time. While the students are exploring and developing their knowledge, they will inevitably run into difficulties, which need to be addressed as they arise. The worksheets are provided to enforce understanding and may be completed in a variety of ways (i.e. group work, as a class, homework, as a “quiz show”), which is up to the discretion of the teacher.

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Lesson Specifics
  • Grade Level: 9th grade Earth Science classroom
  • Time Frame: 50 minutes twice a week for three weeks
  • California State Standard for Chemistry (High School): Atomic & Molecular Structure: "The periodic table displays the elements in increasing atomic number and shows how periodicity of the physical and chemical properties of the elements relates to atomic structure."

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