Heaviest alkali metal to occur in significant quantities

The alkali metals occupy group one, or the left-most column of the periodic table. In order of increasing atomic number they are lithium, sodium, potassium, rubidium, caesium and francium. Although francium, with an atomic number of 87, is heavier than caesium, its minute occurrence on Earth means that you will never see enough francium in one place for it to be visible to the naked eye. Caesium, with an atomic number of 55, is the next metal up from francium in group one of the periodic table. Discovered in 1860, it is silvery gold-coloured and melts at just 28.5 C. Its main uses are as a drilling fluid (in the form of caesium formatted) and electronics. Caesium is one of the most reactive elements in the whole of the periodic table and is highly explosive in water.

n/a