Elements | Properties | lithium | Lithium is the first of the alkalis in the periodic table. In nature it’s found like a mixture of the isotopes Li6 and Li7. It’s the lightest solid metal; it’s soft, silvery-white, with a low melting point and reactive. Many of its physical and chemical properties are more similar to those of the alkaline earth metals than to those of its own group. | Sodium | Chemical element, symbol: Na, atomic number: 11 and atomic weight 22, 9898. It’s a soft metal, reactive and with a low melting point, with a relative density of 0, 97 at 20ºC (68ºF). From the commercial point of view, sodium is the most important of all the alkaline metals. | potassium | Melting temperatures of sodium and potassium to 110 and 145 k bar, respectively, were determined by optical property changes with an externally heated diamond anvil cell using mineral oil as the pressure medium. The pressure was obtained from the known pressure and temperature shifts of the ruby fluorescence line | rubidium | It is one of the most electropositive and alkaline elements. Rubidium can be liquid at ambient temperature, but only on a hot day given that its melting point is about 40°C. It ignites spontaneously in air and reacts violently with water and even with ice at -100 C, setting fire to the liberated hydrogen. | caesium | The metal is characterised by a spectrum containing two bright lines in the blue (accounting for its name). It is silvery gold, soft, and ductile. It is the most electropositive and most alkaline element. Caesium, gallium, and mercury are the only three metals that are liquid at or around room temperature. Caesium reacts explosively with cold water, and reacts with ice at temperatures above -116°C. | francium | Francium is extremely rare. Because of this its chemical and physical properties are not known. It has been studied by radiochemical techniques, which show that it’s most stable state is the ion Fr+. Francium is the least electronegative of all the known elements. |