Francium

Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K.[note 1] It is one of the two least electronegativeelements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Bulk francium has never been viewed. Because of the...

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Caesium

Caesium or cesium[note 1] is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature.[note 2]Caesium is an alkali metal and has physical and chemical properties similar to those ofrubidium and potassium. The metal is extremely reactive and pyrophoric, reacting with water even at −116 °C (−177 °F). It is the least electronegative...

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Rubidium

Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in Group 1, such as very rapid oxidation in air. Rubidium has only one stable isotope, 85Rb. Another isotope, 87Rb, which composes almost 28%...

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