89
Ac
227
Actinium (Ac)
Element 89 · Period 7 · Actinide series
actinide
solid at room temp
f-block
radioactive
About Actinium
First actinoid. Radioactive. Used as neutron source and in radiation therapy.
Physical Properties
Atomic Mass
227 u
State at 25°C
Solid
Melting Point
1050 °C
Boiling Point
3200 °C
Density
10 g/cm³
Magnetism
Paramagnetic
Atomic Properties
Electron Configuration
[Rn] 6d¹ 7s²
Electron Shells
2, 8, 18, 32, 18, 9, 2
Electronegativity
1.1
Atomic Radius
260 pm
Ionization Energy
499 kJ/mol
Oxidation States
+3
Discovery & History
Discovered By
André-Louis Debierne
Discovery Year
1899
Named By
André-Louis Debierne
Name origin: Greek: aktis (beam/ray)
Frequently Asked Questions
- Is Actinium a metal, nonmetal, or metalloid?
- Actinium is classified as a actinide.
- What state is Actinium in at room temperature?
- Actinium is a solid at standard room temperature (25°C).
- What is the atomic mass of Actinium?
- Actinium has an atomic mass of 227 atomic mass units (u).
- Who discovered Actinium?
- Actinium was discovered by André-Louis Debierne in 1899.
- Where is Actinium on the periodic table?
- Actinium is element number 89, located in period 7, part of the actinide series shown below the main table.