Modern Periodic Table: Periods and Groups
Learning Objectives
- Describe the organization of the modern periodic table.
How has the English dictionary evolved over time?

These publications may be in print, or they may be electronic. Dictionaries can be found on the internet and apps are available for smartphones. Dictionaries are invaluable for good, reliable communication.
The figure below shows the most commonly used form of the periodic table. Each square shows the chemical symbol of the element along with its name. Notice that several of the symbols seem to be unrelated to the name of the element: Fe for iron, Pb for lead, etc. Most of these are the elements that have been known since ancient times and have symbols based on their Latin names. The atomic number of each element is written above the symbol.

A group is a vertical column of the periodic table, based on the organization of the outer shell electrons. There are a total of 18 groups. There are two different numbering systems that are commonly used to designate groups and you should be familiar with both. The traditional system used in the United States involves the use of the letters A and B. The first two groups are 1A and 2A, while the last six groups are 3A through 8A. The middle groups use B in their titles. Unfortunately, there was a slightly different system in place in Europe. To eliminate confusion the International Union of Pure and Applied Chemistry (IUPAC) decided that the official system for numbering groups would be a simple 1 through 18 from left to right. Many periodic tables show both systems simultaneously.
Summary
- The periodic table is arranged in order of atomic number
- A period is a horizontal row of the periodic table.
- A group is a vertical row of the periodic table.
Practice
Use the link below to answer the following questions:http://pontotriplo.org/triplepoint/2007/05/the_best_55_online_periodic_tables.html
- Select the periodic table from the “best” column that you like the most. Why did you choose that table?
- Which periodic table in the “specific” section do you like the most? Why?
- Which of the “funny” periodic tables do you like most? Why?
Review
- How is today’s periodic table different from the one that Mendeleev published?
- Are all the elements in today’s periodic table naturally occurring? Explain your answer.
- What is a “period?” What does it represent?
- What is a “group?” What does it represent?
- Why are there two different numbering systems for groups?
Glossary
- group: Elements with similar chemical properties appear at regular intervals, within the vertical columns.
- period: A period is a horizontal row of the periodic table.
Show References
References
- Caleb Roenigk (Flickr:crdotx). http://www.flickr.com/photos/crdot/5510511588/ .
- . . CC BY 2.0