Why Is Hydrogen Placed in Group One of the Periodic Table?
The periodic table is the product of nineteenth century chemists Dmitri Mendeleev, Lothar Meyer, and John Newlands. Elements are placed in rows (periods) and columns (groups) according to atomic number and electron configuration. Hydrogen's placement in the periodic table might appear curious.
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Groups
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The columns, or "groups," of elements represent similar electron configurations. The left-most column, Group One, contains elements with one available, or "valence," electron. Hydrogen has only one electron.
Periods
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The rows are called "periods." From left to right, the quantity of electrons increases, until a "shell" of electrons is complete. Then down one and to the left where the next period begins and the outermost electrons returns to one. Chemical properties approximately repeat.
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Hydrogen
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Hydrogen is at the top of Group One. Historically, that group was named "alkali metals." Grouping hydrogen, a gas, with the alkali metals might seem peculiar; however, a theory suggests hydrogen can behave as a metal.
Hydrogen Metal
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In 1935 Wigner and Huntington theorized hydrogen would be metallic if it were intensely pressurized. Hydrogen should then form a lattice structure and lose control over its individual electrons, like metals. Needed pressures in millions of atmospheres have not yet been attained.
Looking to the Future
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Interestingly, it's predicted metallic hydrogen will be used to launch lunar missions. This is because metallic hydrogen would contain abundant energy.
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- Photo Credit Image by Flickr.com, courtesy of fdecomite
