Alkali Metals

Alkali metals are a group of chemical elements in the first column of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Each of these elements has one electron in its outermost shell, which they readily lose to become ions with a single positive charge.

The name 'alkali' derives from the fact that when these metals are immersed in water, they produce an alkaline hydroxide solution, which is a base. This reaction releases hydrogen gas and heat. The intensity of the reaction increases down the group: lithium reacts in a measured way, while rubidium and cesium react with water violently.

Physical Properties

Alkali metals are soft—some can be cut with a knife. They have low density compared to other metals; lithium, sodium, and potassium float on water. Their melting points are low and decrease further down the group. They conduct electricity and heat well. When freshly cut, their surface is shiny and white, but they tarnish rapidly in air by forming oxides.

Storage and Extraction

Because of their high reactivity, alkali metals do not occur in nature in pure form; they are found in compounds and minerals, such as table salt (sodium chloride). When stored, they are typically kept under mineral oil or an inert gas to protect them from air and moisture. The common method of industrial production is electrolysis of molten salts.

Uses and Biological Role

Sodium and potassium play important roles in living organisms: they regulate water balance and the transmission of nerve signals. Lithium is widely used in rechargeable batteries and in certain psychiatric medications. Cesium is used in atomic clocks that measure global standard time.