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Periodic Table: Alkali Metals
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The 6 elements classified as "Alkaline Earth Metals" are located in Group 2 elements of the Periodic Table. Elements classified as Alkaline Earth Metals are all found in the Earth’s crust, but not in the elemental form as they are so reactive. Instead, they are widely distributed in rock structures. The Alkaline Earth Metals are:
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Besides enhancing the organizing capability of the periodic table, the concept of configuration energy explains many longstanding puzzles about the table itself. It explains the existence of the metalloid band of elements (configuration energy is nearly constant in this band) and why these elements divide the metals from the nonmetals. Elements possessing configuration energies with magnitudes greater than those of the metalloids are nonmetals; those with lower configuration energies are metals. See ... Nonmetal.
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The periodic table can be used by chemists to observe patterns, and relationships between the elements. For example, elements to the top and far left of the table are the most metallic, and elements on the bottom right are the least metallic. (e.g lithium is much more metallic than xenon). There are ... many other patterns and relationships.
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There's nothing artificial about arsenic, which is element No.33 on the periodic table. The most common natural source of arsenic is from specks of metallic minerals, especially pyrite (FeS2; ... known as "fools gold") and a related mineral called arsenopyrite (FeAsS; which could be mistaken for silver).
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Alkali Metals