The chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) form alkali metals. Together with hydrogen, they form the 1st group in the s block of the periodic table. Since all alkali metals have an s-orbital for their outermost electrons, these metals share many of the same physical properties. The group tendencies of the periodic table in properties are best illustrated by alkali metals, whose elements exhibit well-defined homologous behavior. In honor of its main component, this group of elements is often called the lithium family.
At standard temperature and pressure, all shiny, soft, highly reactive alkali metals rapidly eject their outermost electrons to form +1 charged cations. Because of their softness, they can all be easily cut with a knife, revealing a glossy surface that quickly darkens in air due to oxidation by atmospheric moisture and oxygen (and nitrogen in the case of lithium). Due to their strong reactivity, they occur naturally only as salts; they are never found as free elements and must be kept under oil to prevent them from reacting with air. The fifth alkali metal, cesium, is the most reactive metal in existence. Water reacts with all alkali metals, but heavier alkali metals react more strongly than lighter ones.
All newly discovered alkali metals are found in nature as compounds; sodium is the most common in abundance, followed by potassium, lithium, rubidium, cesium, and francium, which is incredibly rare due to its extremely high radioactivity; francium occurs in nature only in extremely small amounts as an intermediate step in some obscure side branches of natural decay chains. Ununennium (Uue), most likely to join the next group, has been attempted to be synthesized in experiments, but none have been successful.
Because of the relativistic effects that are predicted to have a significant effect on the chemical properties of superheavy elements, ununenium may not be an alkali metal; even so, it is predicted to have some different physical and chemical properties from its lighter homologues.
Most of the alkali metals have a wide range of uses. The use of rubidium and cesium in atomic clocks, of which cesium atomic clocks form the basis of the latter, is one of the best-known applications of pure elements. A very good light emitting sodium vapor lamp is a popular application of sodium compounds. Sodium chloride, also known as table salt, has been used since ancient times. Lithium is used both as a psychiatric drug and as an anode in lithium batteries. While other alkali metals are not essential, they have a variety of effects on the body, both good and bad. Sodium, potassium and lithium are essential elements and play important biological roles as electrolytes.
Source: Wikipedia
📩 07/04/2023 17:48
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