Actinium

89
Ac
Group
n/a
Period
7
Block
f
Protons
Electrons
Neutrons
89
89
138
General Properties
Atomic Number
89
Atomic Weight
[227]
Mass Number
227
Category
Actinides
Colour
Silver
Radioactive
Yes
From the Greek aktis, aktinos, meaning beam or ray
Crystal Structure
Face Centered Cubic
History
André-Louis Debierne, a French chemist, discovered actinium in 1899.

He separated it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium.

Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum.
Electrons per shell
2, 8, 18, 32, 18, 9, 2
Electron Configuration
[Rn] 6d1 7s2
Ac
Actinium glows in the dark with a pale blue light
Physical Properties
Phase
Solid
Density
10.07 g/cm3
Melting Point
1323.15 K | 1050 °C | 1922 °F
Boiling Point
3471.15 K | 3198 °C | 5788.4 °F
Heat of Fusion
14 kJ/mol
Heat of Vaporization
400 kJ/mol
Specific Heat Capacity
0.12 J/g·K
Abundance in Earth's crust
n/a
Abundance in Universe
n/a
Illustration
Image Credits: Images-of-elements
Illustration of actinium
CAS Number
7440-34-8
PubChem CID Number
n/a
Atomic Properties
Atomic Radius
-
Covalent Radius
215 pm
Electronegativity
1.1 (Pauling scale)
Ionization Potential
5.17 eV
Atomic Volume
22.54 cm3/mol
Thermal Conductivity
0.12 W/cm·K
Oxidation States
3
Applications
Actinium is used as an active element of radioisotope thermoelectric generators, for example in spacecraft.

The medium half-life of 227Ac makes it very convenient radioactive isotope in modeling the slow vertical mixing of oceanic waters.

225Ac is applied in medicine to produce 213Bi in a reusable generator or can be used alone as an agent for radiation therapy.
Actinium is highly radioactive
Isotopes
Stable Isotopes
-
Unstable Isotopes
206Ac, 207Ac, 208Ac, 209Ac, 210Ac, 211Ac, 212Ac, 213Ac, 214Ac, 215Ac, 216Ac, 217Ac, 218Ac, 219Ac, 220Ac, 221Ac, 222Ac, 223Ac, 224Ac, 225Ac, 226Ac, 227Ac, 228Ac, 229Ac, 230Ac, 231Ac, 232Ac, 233Ac, 234Ac, 235Ac, 236Ac