THE ALKALI METALS ARE A SERIES OF CHEMICAL ELEMENTS FORMING GROUP 1 (IUPAC STYLE) OF THE PERIODIC TABLE: LITHIUM (LI),SODIUM (NA), POTASSIUM (K), RUBIDIUM (RB), CAESIUM (CS), AND FRANCIUM (FR). (HYDROGEN, ALTHOUGH NOMINALLY ALSO A MEMBER OF GROUP 1, VERY RARELY EXHIBITS BEHAVIOR COMPARABLE TO THE ALKALI METALS). THE ALKALI METALS PROVIDE ONE OF THE BEST EXAMPLES OF GROUP TRENDS IN PROPERTIES IN THE PERIODIC TABLE, WITH WELL CHARACTERIZED HOMOLOGOUS BEHAVIOR DOWN THE GROUP.
The alkali metals are all highly reactive and are never found in elemental form in nature. As a result, in the laboratory they are stored under mineral oil or paraffin oil. They also tarnish easily and have low melting points and densities. Potassium and rubidium possess a weak radioactive characteristic due to the presence of long duration radioactive isotopes.
The alkali metals are silver-colored (caesium has a golden tinge), soft, low-density metals, which react readily with halogens to form ionic salts, and wit ...more