© 2008 Chemical Heritage Foundation
The Path to the Periodic Table: Building the Periodic Table
Introduction and Historical Context
Sodium acts a lot like potassium. Silver acts a lot like gold. For a long time scientists have
known that elements seem to be grouped into families with common properties. However, just
which elements belonged together took some time to figure out. Around 1870 two scientists
determined a way to order the elements. Julius Lothar Meyer and Dmitri Mendeleev both came
up with periodic tables that showed how the elements should be grouped.
Meyer lived and worked in Germany, while Mendeleev lived and worked in Russia. Both
scientists were teachers. They hoped that if they could arrange the elements in some way that
made sense, it would be easier for students to learn about all the elements and their properties.
Meyer and Mendeleev worked separately, and neither one knew that the other was working on
a periodic table. Even so, the tables they came up with separately were very similar. The
periodic table we use today is based on the ones they created.
In this activity you’re going to walk in the footsteps of Meyer and Mendeleev. You will be given
cards with the names and properties of elements, and you will be asked to group the different
elements together in a way that makes sense to you.
You will learn how the elements are grouped in the periodic table and what kinds of information
you can obtain by reading the periodic table.
This activity presents no safety hazards.
Materials and apparatus
Element cards provided by your teacher.
1. What is an element? How many different kinds of atom is any element made of?
2. What is the atomic mass of an element?
3. What is the atomic number of an element?
4. How many atoms of each element are present in molecules of the following compounds?
In this activity you will work in teams of three or four people. Your teacher will give each team a
set of cards. Each card in the set will contain information about an element. Your challenge will
be to arrange the cards into a two-dimensional grid in some way that makes sense to you and
the other members of your team. When you have finished arranging your elements, be
prepared to explain to the class why you arranged the element cards the way you did.
1. How many groups or families of elements are in your table?
2. What criteria did you use to choose which group or family an element belongs to?
3. Is there a trend in atomic mass going across your table? Is there a trend in atomic
mass going from top to bottom?
4. Are there any exceptions to these trends? If so, which elements break the trend? Why
did you arrange these elements the way you did?
5. Are there any holes or gaps in your arrangement? Where are they? What do you think
these gaps might mean?
1. After you prepared your periodic tables, your teacher gave you additional sets of cards
to fit into your tables. How did your table change each time you added new elements
to your table?
2. How is your table similar to a modern periodic table? How is yours different?
3. How do we explain today the fact that tellurium comes before iodine in the periodic table,
even though tellurium has a higher atomic mass than iodine?
4. Mendeleev predicted the existence of gallium and germanium because of the holes in his
periodic table. Why do you think Mendeleev did not predict the existence of the noble
5. Look at a modern periodic table. Suppose two new elements were discovered with
the atomic numbers 120 and 121. Where in the periodic table do you think we
would place these new elements?
6. Suppose a new element X is discovered. It forms a compound with chlorine, and the
formula of this compound is XCl4. What group or family do you think this element would
7. Find the element barium (Ba) on a modern periodic table. What group or family is barium
in? What do you think the formula of a compound of barium and chlorine would be?