sentence: Alkali metals are the first group in the periodic table.
sentences_before: Alkali metals' are the chemical elements in group one of the periodic system. They are silver-coloured when pure, soft and have only one electron in the outermost shell. They react strongly with water and because of this, they have to be stored in petrol.
sentences_after: They are never found in nature uncombined because they are unstable and they react fast to other elements. They bond well with all elements except the noble gases. When they are in air, they quickly turn black. They have one valence electron.
concept_name: alkali metal
headings: Alkali metal