astatine

Name astatine
Symbol At
Atomic Weight 209.99
Atomic Number 85
CAS ID 7440-68-8
Group Number 17
Group Name Halogen
Period Number 6
Origin of Name Greek, astatos = "unstable."
Year Discovered 1940
Discovery Credits Produced by D. R. Corson, K. R. Mackenzie, and E. Segre at the University of California, USA.
Class Semi-metallic
Color Metallic Grey
Standard State Solid at 77 F & 298 K
Description Radioactive non-metallic element which does not occur naturally. Relatively unknown because of the short half-life.

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