![]() Johann Wolfgang Döbereiner was among the first to notice similarities between what are now known as the alkali metals. Later that same year, Davy reported extraction of sodium from the similar substance caustic soda (NaOH, lye) by a similar technique, demonstrating the elements, and thus the salts, to be different. : 68 Potassium was the first metal that was isolated by electrolysis. Previous attempts at electrolysis of the aqueous salt were unsuccessful due to potassium's extreme reactivity. Pure potassium was first isolated in 1807 in England by Humphry Davy, who derived it from caustic potash (KOH, potassium hydroxide) by the use of electrolysis of the molten salt with the newly invented voltaic pile. The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus Antoine Lavoisier did not include either alkali in his list of chemical elements in 1789. Georg Ernst Stahl obtained experimental evidence which led him to suggest the fundamental difference of sodium and potassium salts in 1702, and Henri-Louis Duhamel du Monceau was able to prove this difference in 1736. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. Sodium compounds have been known since ancient times salt ( sodium chloride) has been an important commodity in human activities, as testified by the English word salary, referring to salarium, money paid to Roman soldiers for the purchase of salt. History Petalite, the lithium mineral from which lithium was first isolated ![]() Sodium, potassium and lithium are essential elements, having major biological roles as electrolytes, and although the other alkali metals are not essential, they also have various effects on the body, both beneficial and harmful. Lithium finds use as a psychiatric medication and as an anode in lithium batteries. Table salt, or sodium chloride, has been used since antiquity. A common application of the compounds of sodium is the sodium-vapour lamp, which emits light very efficiently. One of the best-known applications of the pure elements is the use of rubidium and caesium in atomic clocks, of which caesium atomic clocks form the basis of the second. Most alkali metals have many different applications. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of superheavy elements even if it does turn out to be an alkali metal, it is predicted to have some differences in physical and chemical properties from its lighter homologues. Experiments have been conducted to attempt the synthesis of element 119, which is likely to be the next member of the group none were successful. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.Īll of the discovered alkali metals occur in nature as their compounds: in order of abundance, sodium is the most abundant, followed by potassium, lithium, rubidium, caesium, and finally francium, which is very rare due to its extremely high radioactivity francium occurs only in minute traces in nature as an intermediate step in some obscure side branches of the natural decay chains. Caesium, the fifth alkali metal, is the most reactive of all the metals. Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free elements. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. This family of elements is also known as the lithium family after its leading element. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. ![]() Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. ![]() The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
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