The Periodic Table

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Dimitri Mendeleev is credited with the organization of the periodic table. He was arranging the elements based on their experimental properties and reactivity. It turns out that there is an underlying reason to the periodic repetition of properties. Elements with similar properties have the same valence shell electron configuration. We will explore the periodic table in more detail in the next unit on periodic trends. At this point, you should be able to connect the position on the periodic table to the electron configuration. In fact, the periodic table is a cheat sheet of sorts for electron configuration. As you see in the figure to the right, the order of filling is exactly how the elements are arranged in the periodic table. The s-block elements (groups 1 & 2) have ns valence electrons and the p-block elements (groups 3-8) add np electrons to the valence shell. The 3d electrons are not filled until after the 4s, and so on.

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