The current periodic table (as of January 2008) contains 117 elements, and is ubiquitous within the discipline of chemistry, because it is such a useful framework for comparing many different forms of chemical behavior. The table is also widely used in physics, biology, engineering, and industry.

The Periodic Table has groups, and periods. A group is a vertical column in the periodic table of the elements which is considered the most important method of classifying the elements. A period is a horizontal row in the periodic table of the elements. While groups are the most common way of classifying elements, there are some areas of the periodic table where horizontal trends are more significant than vertical group trends.