Actinium

Actinium (Ac)

Silvery radioactive metallic element, belongs to group 3 of the periodic table. The most stable isotope, Ac-227, has a half-life of 217 years. Ac-228 (half-life of 6.13 hours) also occurs in nature. There are 22 other artificial isotopes, all radioactive and having very short half-lives. Chemistry similar to lanthanumpy. Used as a source of alpha particles. Discovered by A. Debierne in 1899.
Atomic Number89
Atomic Weight227
Mass Number206
Group3
Period7
Blockd
Protons89 p+
Neutrons117 n0
Electrons89 e-
Actinium sample (31481701837).png Electron shell 089 Actinium.svg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
195 pm
Atomic Volume
22.54 cm³/mol
Covalent Radius
186 pm
Metallic Radius
Ionic Radius
112.00000000000001 pm
Crystal Radius
126 pm
Van der Waals radius
247.00000000000003 pm
Density
Boiling Point
3,470 K
Melting Point
1,320 K
Electrons per shell2, 8, 18, 32, 18, 9, 2
Electronegativity
1.1
Electrophilicity
0.8159546412794 eV/particle
Proton Affinity
Electron Affinity
Ionization Potential
5.380226 eV/particle
Heat of Vaporization
292.9 kJ/mol
Heat of Fusion
10.5 kJ/mol
Heat of Formation
406 kJ/mol
Molar Heat Capacity
Specific Heat Capacity
Thermal Conductivity
Gas Basicity
Dipole Polarizability
203 a₀
C6 Dispersion Coefficient
Oxidation States3
Color
Silver
Crystal StructureFace Centered Cubic (FCC)
Lattice Constant
5.31 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Rn] 6d1 7s2
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryActinides, Actinides
CAS GroupIIIA
IUPAC GroupIIIB
Glawe Number33
Mendeleev Number14
Pettifor Number48
Geochemical ClassU/Th decay series
Goldschmidt Classsynthetic
Radioactivity
RadioactiveYes ☢️
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
0.00000000055 mg/kg
Abundance in Oceans
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universena

Isotopes of Actinium

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

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. From the Greek aktis, aktinos, meaning beam or ray

DiscoverersAndré Debierne
Discovery LocationFrance
Discovery Year1899
Name OriginGreek: akis, aktinos (ray).
Actinium is highly radioactive
Actinium glows in the dark with a pale blue light

Uses

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. It has no significant commercial applications.

Sources

Extremely rare, found in all uranium ores. Usually obtained by treating radium with neutrons in a reactor.