Name actinium
Symbol Ac
Atomic Weight 227.03
Atomic Number 89
CAS ID 7440-34-8
Group Number
Group Name Actinoid
Period Number 7
Origin of Name From the Greek, aktinos = "ray."
Year Discovered 1899
Discovery Credits Discovered by A. Debierne at Paris, France.
Class Metallic
Color Silvery
Standard State Solid at 77 F & 298 K
Description Soft, Silvery-white metal which glows in the dark. Reacts with water to evolve H2. Primarily occurs as a trace amount (a few ppm) in uranium minerals where it is a decay product of U238

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