When deciding on a periodic table lab activity, one of the most important skills you want your students to gain is the ability to identify trends in a complex representation such as the periodic table. Groupwork is most helpful for this type of activity, so that students can share ideas and help each other generate and test possible trends. Have students graph various aspects of the elements of the periodic table, taking into account any two related variables, such as atomic radius and atomic number, ionization energy and atomic number, or even something as basic as atomic mass and atomic number. Then have them draw conclusions based on the graphs. Alternatively, have them make two-column charts comparing and contrasting any two elements or groups of elements. Although younger students may find it easier to work with two specific elements, more advanced students should be encouraged to look at generalized groups, such as noble gases and another family of elements. They should then draw conclusions about those similarities and differences exist between the two groups of elements.
Instead of explaining the different sections of the periodic table and describing how they differ from each other, encourage students to use hands-on methods to figure these things out themselves. This will help students connect the information in the periodic table to tangible objects. Give groups samples of several different elements, including metals, nonmetals and metalloids. Then encourage students to create a chart that can include information about each element's appearance, conductivity, ability to be crushed and reactivity with hydrochloric acid. Provide students with a small hammer, a conductivity tester and some hydrochloric acid, and instruct them to complete the chart. Then have them evaluate whether they think each element is a metal (which has a luster, is malleable, conducts electricity and often reacts with acids), a nonmetal (which usually has a duller appearance, is more easily crushed and does not conduct electricity) or a metalloid (which contains some aspects of a metal and some of a nonmetal). Compare their results with the rest of the class. In this way, students will be acting like scientists and using what they've learned about the periodic table to make inferences about tangible materials.