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Astatine (At)

Astatine (At) is element 85 of the periodic table, a halogen in period 6 and group 17. It has no stable isotope and no standard atomic weight; 210 is the mass number of its longest-lived isotope. At room temperature it is a solid.

85 At Astatine [210]

Period 6, group 17 · Halogen

← Po Polonium Rn Radon →

Atomic number	85
Symbol	At
Standard atomic weight	[210] (mass number of the longest-lived isotope)
Molar mass	[210] g/mol
Category	Halogen
Group	17
Period	6
Block	p-block
Electron configuration	[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁵
Oxidation states	+7, +5, +3, +1, −1
Electronegativity (Pauling)	2.2
Atomic radius (van der Waals)	202 pm
First ionisation energy	9.5 eV (916.6 kJ/mol)
Electron affinity	2.8 eV
State at room temperature	Solid
Melting point	575 K (301.85 °C)
Boiling point	—
Density	7 g/cm³
Discovered	1940

Group 17

F · Fluorine Cl · Chlorine Br · Bromine I · Iodine Ts · Tennessine

Calculate with Astatine

Molar mass of At Balance an equation Grams, moles and particles Whole periodic table

Atomic weight: IUPAC CIAAW — no standard atomic weight; mass number in brackets. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.