OCCURENCE

Since the alkali metals are the most active metals, they are not found free in nature, but as compounds. Generally they occur in sea water, in some lakes, in rock salt sources and in the compounds of oxygen and silicon as silicates.

Sodium and potassium are present in vast amounts in nature.The most important compound of sodium is sodium cloride, NaCl. It is found in the form of NaCl in the seas and in rock-salt layers formed by the evaporation of ancient lakes and seas. The important sodium sources are Chile saltpeter, washing soda (Na2C03) and baking soda (NaHC03). The most important sodium minerals are kryolite, borax, sodium sulfate and albite. Potassium constitutes 1.5% of the earth's crust. Potassium is found as the minerals sylvite (KC1) and carnallite (KC1 • MgCl2 • 6H20) and as the silicates of orthoclas (KAlSi308) and mica (KH2Al3(Si04)3). The main sources of potassium are K2S04 and KN03, which are used as fertilizers.

Sodium Lithium is less abundant in comparison with sodium and potassium. Lithium is found in nature in the ores petalite, spodumene amblygonite and lepidolite. Rubidium and cesium are found in trace amount in nature. Francium, a radioactive element, is a side product and all isotopes of francium are also radioactive.

Sodium lamps are used in street lamps and in cars. When it is foggy, they emit yellow light.

USES

Lithium is used to eliminate poisonous gases from copper and copper alloys. Some lithium compounds are used as medicine, such as Li2C03 in psychiatry and LiHC03 in the treatment of hyperureacemia. LiCI is a drying agent and LiAIH4 is used as a reducing agent in organic reactions. Sodium is used to produce electricity in nuclear reactors by transferring excess heat to the vapor turbines. In metallurgy, it is used to produce pure metals from their oxides. It is also used in sodium vapor lamps for foggy days. Its salts are used in the medical industry. In industry, it has an important role in the production of salts, soaps, baking soda, glass and pigment. Potassium is mostly used in fertilizers, producing soaps, and medicine in several areas. The soaps in which potassium is used are very soft and have the common name gel. Since rubidium and cesium emit electrons by photocell rays, they are used as photocells. They are used in TV receivers, as a prism in spectrophotometers, and as propellants in space ships. In these processes, cesium is used rather than rubidium.

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Alkali metals. INTRODUCTION	\|	SUPPLEMENTARY QUESTIONS

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