| 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 |