Name: astatine
Symbol: At
Atomic number: 85
Atomic weight: [ 210 ]
Group in periodic table: 17
Group name: Halogen
Period in periodic table: 6
Block in periodic table: p-block
CAS registry ID: 7440-68-8
The longest-lived isotope, 210At, has a half-life of only 8.3 hours. There are about 20 isotopes known, all of which are radioactive. Astatine is a halogen and possibly accumulates in the thyroid like iodine.