Based on previous experience, students have difficulty conceptualizing atomic orbitals. In middle school science classes as well as popular culture, atoms are generally represented through Bohr’s planetary model. This representation shows a nucleus of protons and neutrons with electrons orbiting around in set orbits. Students also have many other examples they can think of in regards to orbits—such as the planets around the sun. This is the image that has been taught and the image they are used to. The quantum mechanical model presents a challenge for instruction for these reasons. Students have to change their entire conceptual understanding of how the atom is structured. The electrons are not circling in fixed orbits. Instead they occupy orbitals—a region of space, which an electron is likely to occupy. Orbitals incorporate probability—a concept which many of my students have little to no experience with. An orbital does not tell you the specific location of an electron. Rather it tells you the area of space that an electron most likely occupies at any given time. There are also four primary orbitals—s, p, d, and f—each with different shapes and capacity to hold electrons. These orbitals can occupy the x-axis, y-axis, and z-axis. Many of my students lack foundational math and graphing skills. They have major gaps in knowledge in this content area. Many do not know which is the x-axis and which is the y-axis. Also the majority of 10th grade students have never been exposed to the z-axis in their math classes yet. Orbitals are also a 3-dimensional space but are frequently represented by diagrams on paper. Another mental block for students—similar to the majority of concepts in chemistry—is that atomic orbitals are too small to actually see. We can diagram them but we cannot physically see them. All of these reasons, in combination, make mastering a conceptual understanding of atomic orbitals difficult for many students. For this reason, the guided practice portion of this lesson aims to give students a hands-on experience “building” atomic orbitals that they can physically see and touch.

In this section of the lesson, students—working with their purposefully assigned table partners—construct representations of atomic orbitals out of balloons. We cover one of the four primary orbitals (described in the “Introduction to New Material” section above) and then students have the opportunity to “build” the orbital. While students are constructing their models, I can circulate the room answering questions as necessary. I can also ensure that all students are building their models correctly. There are embed frequent check for understanding questions to ask groups while I walk around. When every partner pair has a properly constructed model, we can move on to the next orbital. Through this step-by-step process, I can make sure no student is falling behind and we are all progressing at the same pace. “A common and dangerous mistake during the Guided Practice phase of the lesson cycle is to allow one student to serve as a representative for the entire class, leaving the rest of the students without adequate engagement with the material” (Teach for America, 2011, p. 89). This lesson was designed to ensure all students are required to think and participate. When designing this activity, I realized there could be an issue with accountability. It was entirely possible that one student in the partner pair would build the entire model and the other partner would be left not understanding. Multiple colors of balloons are used to solve this issue and increase accountability. The partner with the longer hair is given only black balloons. The partner with the shorter hair is given only while balloons. Each model involves blowing up, tying off, and connecting two or more balloons. Students are required to alternate which color of balloon they add to their model. Students are also not allowed to tie on a balloon that is not their color. This allows me to ensure all students are participating. Models should be a mix of black and white balloons. I should also never see one of the partners using the color balloon that was not assigned to them. This activity relates directly to the selected Common Core State Standards, which requires collaboration between students. 

Problems during a lesson should be scaffolded from easy to more difficult (Teach for America, 2011). During this lesson, students start by using a single balloon to construct the circular sphere of the “s” orbital. This is a fairly easy mental picture for students to create even without a model. By the end of the lesson students are constructing the significantly more difficult shape of three “p” orbitals together, which uses many balloons and utilizes the concepts of the x-axis, y-axis, and z-axis. 

Before students begin to build each balloon model I verbally remind them of the lesson objective because it is important to be clear how an activity aligns to the daily objective (Teach for America, 2011).

The main purpose of Guided Practice is to allow student a safe environment to practice using their new knowledge and skills (Teach for America, 2011). I can constantly monitor student progress, correcting misconceptions, and reteaching as necessary to clear up any confusion. Each atomic orbital model acts as a type of formative assessment. I can easily determine if students correctly comprehended the desired atomic orbital. If they did not build the structure correctly, I can demonstrate and close gaps in knowledge. “Checks for Understanding are a critical component of every step of your lesson plan” (Teach for America, 2011, p. 93). For this reason, CFUs have been incorporated as frequently as possible during this lesson. 

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This lesson was also designed to operate through the system of “I do,” “we do,” “you do” (Lemov, 2010). At first, I show the student the atomic orbital. I have a pre-built model to show them—I do. Then we walk through building the orbital as a class—we do. Finally, students work with their partner to build their own model—you do.