We're going to be honest: we do Physics. That's why this is called The Physics Classroom website. And when we do the Teacher's Notes section for our Concept Builders, we typically have a lot to say ... and a lot of resources to point you to. We're not claiming to be ignorant of chemistry; we just don't have a lot of resources here at The Physics Classroom to point you to. And so this page is going to be a lot shorter than our usual page that accompanies our Physics Concept Builders. That's our honest confession.

Most chemistry courses will spend some time emphasizing the patterns that exist for various properties of elements as one goes from element to element across a period or down a group in the periodic table. These so-called periodic properties are the basis of the organization of elements in the periodic table. Such properties include atomic radius, ionization energy, electronegativity, electron affinity, melting point, boiling point, and more. This activity challenges students to use an understanding of the trends in three of the properties in order to rank three elements according to the value of that property. The three periodic properties are atomic radius, ionization energy, and electronegativity.

Like all our Concept Builders, this Concept Builder utilizes a variety of strategies to make each student's experience different. The ordering of questions is random. The Question number assigned to each question is scrambled. For instance, two side-by-side students will not have the same question for question number three. And questions are organized into Question Groups with questions within the same group being very similar (for instance, they have the same type of information as "givens") but not identical. 

The Concept Builder also keeps track of student progress. It requires that students demonstrate a mastery of questions in each Question Group. If they miss a question from one group, then they will have to answer two consecutive questions correctly in order to demonstrate mastery. Progress is displayed in the progress report on the right side of the Concept Builder. 

This Concept Builder consists of three separate activities. Each activity focuses on a separate periodic property. The first activity - Atomic Radius -consists of six Question Groups that target student understanding of patterns in the size (or atomic radius) of atoms. Students are presented with three elements and must rank those three elements according to their atomic radius. Two of the Question Groups will present three elements that are located in the same group. Two of the Question Groups will present elements that are located in the same period. And finally, two of the Question Groups will present students with three elements, two of which are in the same group and the third of which is in the same period as the lowest element in that group.

The second activity - Ionization Energy -and the third activity - Electronegativity - are similar to the first activity. There are six Question Groups in these two activities with each question involving the task of ranking three elements according to a periodic property. The same set of three elements are used in the second and third activity as were used in the first activity. Students must rank the three elements according to their ionization energy or their electronegativity. In all activities, the elements were chosen so as to emphasize the general trend in the properties and not any of the particular exceptions that could be found.

In order to complete an activity, a student must correctly analyze each question of that activity. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the activity. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through an activity, a system of stars and other indicators are used to indicate progress on the activity. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question of a difficulty level has been analyzed, the student earns a Trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned activities.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise.