Atomic number 89
Actinium
Actinide
No photo: here’s why
Actinium is so radioactive it glows faintly blue in the dark. It exists only in tiny lab-made amounts and is never seen outside shielded research.
Quick facts
- Atomic mass
- 227.00
- Group
- –
- Period
- 7
- State (STP)
- solid
- Electronegativity
- 1.10
- Common ox. states
- +3
Properties
[Rn] 6d¹ 7s²
- Ionization energy
- 499.0 kJ/mol
- Electron affinity
- –
- Melting point
- 1323.00 K (1049.8 °C)
- Boiling point
- 3473.00 K (3199.8 °C)
How dangerous is it?
So radioactive it makes the air around it glow a faint blue, yet it exists only in tiny amounts inside specialist labs.
- RadioactiveImmediate and cumulative
It pours out alpha radiation many times faster than radium, so a speck carries a real punch if it gets inside the body. (most dangerous if inhaled or swallowed, when the alpha radiation reaches living cells)
Studied only in shielded gloveboxes by licensed labs, handled remotely behind heavy screening.
How it bonds· family overview
Actinium (Ac) is an actinide. Like the lanthanides it tends toward a +3 oxidation state, but the early actinides (Th–Am) routinely access +4, +5, +6, even +7 because the 5f electrons are easier to ionize. Most actinides are radioactive; their "bonding" in school is read off the periodic table, not measured in lab.
