Alkali Metals

The chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium make up the alkali metals (Fr). They make up group 1, which is located in the s-block of the periodic table, along with hydrogen. Since all alkali metals have an s-orbital for their outermost electron, these metals share a lot of the same physical characteristics. The periodic table's group trends in characteristics are best shown by the alkali metals, whose elements display well-defined homologous behaviour. Due to their softness, they are all readily sliced with a knife, revealing a bright surface that tarnishes quickly in the air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). They are only found naturally as salts and never as the free elements, and must be preserved under oil to prevent reactivity with air. The most reactive metal is caesium, the sixth alkali metal. The heavier alkali metals react more forcefully than the lighter ones with water than the other alkali metals.