Introduction group Ia
The alkali metals (Lithium Li, Natrium Na, Potassium K, Rubidium Rb, Cesium Cs, Francium Fr) form a homogeneous group of extremely reactive elements which illustrate well the similarities and trends to be expected from the periodic classification. Their physical and chemical properties are readily interpreted in terms of their simple electronic configuration, and for this reason they have been extensively studied by the full range of experimental and theoretical techniques.
Compounds of sodium and potassium have been known from ancient times and both elements are essential for animal life. They are also major items of trade, commerce and chemical industry.
Lithium was first recognized as a separate element at the beginning of the nineteenth century but did not assume major industrial importance until about 40 years ago.
Rubidium and cesium are of considerable academic interest but so far have few industrial applications.
Francium, the elusive element 87, has only fleeting existence in nature due to its very short radioactive half-life, and this delayed its discovery until 1939.
