Alkali Metals (Encyclopedia of Science)
The alkali metals are the elements that make up Group 1 of the periodic table: lithium, sodium, potassium, rubidium, cesium, and francium. These elements are all much too active to exist in nature in their native state. However, they do form a number of important compounds, such as table salt (sodium chloride), borax (sodium tetraborate), potash (potassium carbonate), and washing soda (sodium carbonate).
Because the alkali metals all have one electron in the outer orbit of their atoms, they have similar chemical and physical properties. All are shiny, soft enough to cut with a knife, andith the exception of cesiumhite. They all react with water vigorously to form hydrogen gas and the hydroxide of the metal. As an example, when potassium metal is added to water, it floats on top of the water and produces an extreme reaction. In fact, so much heat is released that the hydrogen gas produced in the reaction begins to burn.
The usual method for detecting compounds of the alkali metals is with a flame test. A platinum wire is dipped into a solution of the unknown compound and then placed into a hot flame. The color produced is characteristic of the alkali metal present. The lithium flame is bright red; sodium, yellow; potassium, violet; rubidium, dark red; and cesium, blue.
The compounds of lithium, sodium, and rubidium have a number of important practical...
(The entire section is 766 words.)
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