Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902.
Read key information and facts about element Actinium
|Group in Periodic Table||N/A|
|Period in Periodic Table||7|
|Block in Periodic Table||f-block|
|Electronic Configuration||[Rn] 6d1 7s2|
|Melting Point||1050 °C|
|Boiling Point||3200 °C|
|Electronic Shell Structure||[2, 8, 18, 32, 18, 9, 2]|
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 89 to find Actinium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Actinium on periodic table look for cross section of group N/A and period 7 in the modern periodic table.
The element Actinium was discovered by Friedrich Oskar Giesel in year 1899 in France . Actinium derived its name from the Greek aktis, 'ray'
The table below shows the abundance of Actinium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
|Ppb by weight (1ppb =10^-7 %)|
|Abundance in Universe||N/A|
|Abundance in Sun||None|
|Abundance in Meteorites||N/A|
|Abundance in Earth's Crust||N/A|
|Abundance in Oceans||N/A|
|Abundance in Humans||None|
The solid state structure of Actinium is Face Centered Cubic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
and the angles between them Lattice Angles (alpha, beta and gamma).
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
|Space Group Name||Fm_ 3m|
|Space Group Number||225|
|Crystal Structure||Face Centered Cubic|
Actinium atoms have 89 electrons and the electronic shell structure is [2, 8, 18, 32, 18, 9, 2] with Atomic Term Symbol (Quantum Numbers) 2D3/2.
|Number of Electrons (with no charge)||89|
|Number of Protons||89|
|Number of Neutrons||138|
|Shell structure (Electrons per energy level)||[2, 8, 18, 32, 18, 9, 2]|
|Electron Configuration||[Rn] 6d1 7s2|
|Valence Electrons||6d1 7s2|
|Atomic Term Symbol (Quantum Numbers)||2D3/2|
Shell Structure of Actinium - Electrons per energy level
The ground state electronic configuration of Neutral Actinium atom is [Rn] 6d1 7s2. The portion of Actinium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Rn]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used.This is important as it is the Valence electrons 6d1 7s2, electrons in the outermost shell that determine the chemical properties of the element.
Complete ground state electronic configuration for the Actinium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p6 6d1 7s2
Actinium atomic radius is 195 pm, while it's covalent radius is N/A.
195 pm (1.95 Å)
|Atomic Volume||22.542204568 cm3|
|Van der Waals Radius||N/A|
|Neutron Cross Section||810 σa/barns|
The electron affinity of Actinium is N/A
Refer to table below for Ionization energies of Actinium
|Ionization energy number||Enthalpy - kJ/mol|
Refer to below table for Actinium Physical Properties
|Molar Volume||22.542204568 cm3|
Actinium is N/A of electricity. Refer to table below for the Electrical properties of Actinium
|Thermal Conductivity||12 W/(m K)|
|Mass Magnetic Susceptibility||N/A|
|Molar Magnetic Susceptibility||N/A|
|Volume Magnetic Susceptibility||N/A|
|Speed of Sound||N/A|
Refer to table below for Thermal properties of Actinium
|Melting Point||1323 K (1050 °C)|
|Boiling Point||3473 K (3200 °C)|
|Heat of Fusion||14 kJ/mol|
|Heat of Vaporization||400 kJ/mol|
|Heat of Combustion||N/A|
Isotopes of rhodium. Naturally occurring Actinium has 1 stable isotope - None.
|Isotope||Isotope Mass||% Abundance||T half||Decay Mode|
|DOT Hazard Class||N/A|
|NFPA Fire Rating||N/A|
|NFPA Health Rating||N/A|
|NFPA Reactivity Rating||N/A|
List of unique identifiers to search the element in various chemical registry databases
|CAS Number - Chemical Abstracts Service (CAS)||CAS7440-34-8|
|Alkali Metals||Alkaline Earth Metals|
|Transition Metals||Post-Transition Metals|