Secret in the Margins: Rutherford's Gold Foil Experiment.

[ILLUSTRATION OMITTED] "I think that scientists are pretty certain about the structure of an atom because they have been studying it for many years. Scientists have seen the atom through microscopes and have even been able to determine its molecular structure." The quote above is a student's misguided response to the question: "How certain are scientists of the structure of the atom?" How would your students answer this question? Their answers--and the misconceptions they contain--might surprise you. All too often, science lessons focus on what we know, but not how we know it. Research shows that students often have trouble understanding how scientists come to know the world and how scientific knowledge is generated (Lederman 2007). They also tend not to develop nature of science (NOS) understandings implicitly--even when engaging in inquiry activities (Abd-El-Khalick 2002; Abd-El-Khalick and Lederman 2000). But, to teach NOS effectively, teachers don't have to add another unit to an already crowded curriculum: Instead, they can emphasize elements of NOS and incorporate the history of science into their science content (AAAS 1993; Kirchhoff 2008). In this article, we describe a lesson that uses the 5E--Engage, Explore, Explain, Elaborate, and Evaluate--Learning Cycle (Bybee 1997) to help students not only understand the atomic model but also how Ernest Rutherford helped develop it. The lesson uses Rutherford's gold foil experiment to focus on three aspects of NOS: the empirical nature of science, the tentativeness of scientific knowledge, and the distinction between observation and inference. Rutherford and the NOS A unit on atomic structure is a good place to stress both the history and nature of science (Craft and Miller 2007). The National Science Education Standards recommend the use of history in school science programs to "clarify different aspects of scientific inquiry, the human aspects of science, and the role that science has played in the development of various cultures" (NRC 1996, p. 107). Ernest Rutherford, creator of the nuclear atomic model and father of nuclear physics, holds a special place among researchers who study the atom. And we think the story of his life, studies, creativity, and experiments can enrich your teaching and facilitate students' understanding. The following sections explain each phase of our 5E atomic model lesson in more detail. Engage The purpose of this phase of the learning cycle is to pique students' interest and activate their prior knowledge. To begin, have students participate in a "black box" activity. The term black box refers to a system with inner workings that cannot be directly observed, such as an atom or planet Earth. (There are many variations of this common activity available online [see "On the web"].) Before class, prepare some boxed and wrapped "presents" that include objects of varying shapes and weights. To make the activity even more challenging, construct partitions within each box. The number of boxes will depend on the number of students in your class. When class begins, have students imagine that they've received a present they are not allowed to open, but really want to figure out what's inside. What might they do? From our experience, students generally suggest shaking the present, weighing it, examining its shape, measuring it, or checking its firmness at various points. After discussing potential approaches, divide students into groups of three or four. Provide each with a "present" and have them try to figure out what's inside (without opening it!). You can also give groups a list of possible presents, including some items that aren't wrapped, but they should not be easily guessed by their shape or weight. Key chains, magazines, calendars, coffee mugs, hats, a couple of gloves or socks, and candles work well. [FIGURE 1 OMITTED] Each group then shares what they think is inside the box and the evidence on which they've based their conclusions. …