Ununennium - ₁₁₉Uue: the essentials

• Name: ununennium
• Symbol: Uue
• Atomic number: 119
• Relative atomic mass (A_r): [ ?]
• Standard state: presumably a solid or liquid at 298 K
• Appearance: unknown, but probably metallic and silvery white or grey in appearance
• Classification: Metallic

• Group in periodic table: 1
• Group name: Alkali metal
• Period in periodic table: 8
• Block in periodic table: s
• Shell structure: 2.8.18.32.32.18.8.1
• CAS Registry: 54846-86-5

Ununennium, also known as element 119 (or eka-francium), is the as yet unknown chemical element with atomic number 119 and symbol Uue. Ununennium and Uue are the temporary systematic IUPAC name and symbol, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkali metal, and the first element in the eighth period.

Ununennium is the first element that has not yet been synthesized. To date, all attempts to synthesize this element have been unsuccessful. Its position as the seventh alkali metal suggests that it would have similar properties to the alkali metals, lithium, sodium, potassium, rubidium, caesium, and francium; however, relativistic effects may cause some of its properties to differ from those expected from a straight application of periodic trends. For example, ununennium is expected to be less reactive than caesium and francium and be closer in behavior to potassium or rubidium, and while it should show the characteristic +1 oxidation state of the alkali metals, it is also predicted to show the +3 oxidation state unknown in any other alkali metal.