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Actinium , including Technical Data, Safety Data and its high purity propertiesresearch, applications and other useful facts are discussed below. Scientific facts such as the atomic structure,ionization energyabundance on Earthconductivity and thermal properties are included.

Actinium is a radioactive metal that is silvery-white in appearance. Rapidly reacting with the combination of moisture in the air and oxygen, Actinium forms a white coating of actinium oxide which prevents further oxidation. Rarely occurring naturally in the Earth’s crust, Actinium can be made in the lab, but has very minimal important uses.

Actinium is an F-Block, Period 7 element. The number of electrons in each of Actinium‘s shells is 2,8,18,32,18,9,2 and its electronic configuration is [Rn] 6d17s2. In its elemental form Actinium‘s CAS number 7440-34-8. The actinium atom has a radius of 195 pm.


First was noted as a new element by a French chemist, André-Louis Debierne, in 1899. Actinium was discovered again as an independent element in 1902 by German chemist Friedrich Oskar Giesel.

Abundance. The following table shows the abundance of actinium and each of its naturally occurringisotopes on Earth along with the atomic mass for each isotope.
Isotope Atomic Mass % Abundance on Earth
Ac-224 224.021708 -
Ac-225 225.02322 -
Ac-226 226.026089 -
Ac-227 227.027750 (3) -
Ac-228  228.031104 -
Ac-229 229.03293 -

The following table shows the abundance of actinium present in the human body and in the universe scaled to parts per billion (ppb) by weight and by atom:

  Typical Human Body Universe
by Weight - 0
by Atom - -

Ionization Energy. The ionization energy for actinium (the least required energy to release a single electron from the atom in it‘s ground state in the gas phase) is stated in the following table:
1st Ionization Energy 499 kJ mol-1
2nd Ionization Energy 1170 kJ mol-1

Conductivity. As to actinium ‘s electrical and thermal conductivity, the electrical conductivity measured in terms of electrical resistivity @ 20 ?C is10-8 ?Ocm and its electronegativities (or its ability to draw electrons relative to other elements) is 1.1. The thermal conductivity of actinium is 12 W m-1 K-1. 

Thermal Properties. The melting point and boiling point for actinium are stated below. The following chart sets forth the heat of fusion, heat of vaporization and heat of atomization.
Heat of Fusion 14.2 kJ mol-1
Heat of Vaporization 400 kJ mol-1
Heat of Atomization 406 kJ mol-1

Formula Atomic Number Molecular Weight Electronegativity (Pauling) Density Melting Point Boiling Point Vanderwaals radius Ionic radius Energy of first ionization
Ac 89 [ 227 ] 1.1 10.07 g/cm3 1050 °C 3199 °C   112 pm 499 kJ.mol-1