The Periodic Table


The periodic table is the most powerful tool chemists have for organizing chemical information. Without it, chemistry would be a chaotic, confusing jumble of seemingly random observations. What makes the periodic table really invaluable is its use as a predictive tool. You can predict a lot about the chemical behavior of an element if you know where it is on the periodic table. We give credit to Dmitri Mendeleev for the first Periodic Table. He organized the elements in his table in order of atomic mass. Henry Moseley modified the table, ordering the elements in terms of atomic number. This is the periodic table we use today.

There are 92 naturally occurring elements on Planet Earth, but they don’t all behave in the same way, chemically. Some elements are metals, some are non-metals, and others are somewhere in between. Some materials react with each other, while some are inert. How can we make sense of the various observations of their chemical behavior?

The periodic table brings order to the chaos of seemingly random observations about the chemical elements. Most importantly, the periodic table serves as a predictive tool. Based on the location of an element in the periodic table, you can predict a lot about its chemical behavior.

The periodic table as we know it evolved over time, as more information was uncovered about the various elements. In 1869, Dmitri Mendeleev developed the first modern Periodic Table, with the elements ordered by increasing atomic mass. An important refinement came in 1913, when Henry Mosely reordered the elements by increasing atomic number.

This video presents the following essential details about the Periodic Table:

  • The contributions of scientists including Mendeleev, Meyer, and Moseley
  • The periodicity of chemical behavior and Periodic Law
  • Groups or Families (vertical columns) and Periods (rows)
  • Where to find the alkali metals, alkaline earth metals, transition metals, metalloids, halogens, and noble gases
  • Updates to the Periodic Table through history

The subject of Periodic Trends will be featured in its own separate video (under production).
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Video: The Periodic Table

Handout: Video Notes Worksheet

Interactive Quiz

Practice Test: The Periodic Table & Periodic Trends