Ac
Actinium
Element 89 · 227.02775 u
Actinium is the namesake of the actinide series and glows blue in the dark.
Physical Properties
| Atomic Mass | 227.02775 u |
| Density | 10.07 g/cm³ |
| Melting Point | 1323.0 K |
| Boiling Point | 3471.0 K |
| Appearance | Silvery-white metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 1.1 (Pauling) |
| 1st Ionization Energy | 499.0 kJ/mol |
| Electron Affinity | 33.77 kJ/mol |
| Oxidation States | +2, +3 |
Atomic Properties
| Electron Configuration | [Rn] 6d1 7s2 |
| Atomic Radius | 195.0 pm |
| Van der Waals Radius | 260.0 pm |
Discovery
| Discovered By | Friedrich Oskar Giesel, Andre-Louis Debierne |
| Discovery Year | 1899 |
| Location | Paris, France |
| Named After | Greek 'aktis' meaning ray or beam |
About Actinium
Actinium is a soft, silvery-white radioactive metal that glows blue due to its intense radioactivity ionizing the surrounding air. Actinium-225 is being researched for targeted alpha therapy against cancer.
Uses & Applications
Neutron sources, cancer research (actinium-225), and thermoelectric generators.
Fun Fact
Actinium is so radioactive it visibly glows blue in the dark from ionizing the surrounding air.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 225 | - | 10.0 days | No |
| 227 | - | 21.772 years | No |
Electron Configuration
[Rn] 6d1 7s2