What is the boiling point of actinium

Name, symbol, atomic number Actinium, Ac, 89
Group, period, block3, 7, f
Look silvery
Mass fraction of the earth's envelope 6 · 10−14 %
Atomic mass 227.0278 u
Atomic radius (calculated) 195 (-) pm
Covalent radius - pm
Van der Waals radius - pm
Electron configuration [Rn] 6d17s2
Electrons per energy level 2, 8, 18, 32, 18, 9, 2
1. Ionization energy 499 kJ / mol
2. Ionization energy 1,170 kJ / mol
Physical state firmly
Modifications -
Crystal structure Cubic area-centered
density 10.07 g / cm3
Melting point 1323 K (1050 ° C)
boiling point 3473 K (3200 ° C)
Molar volume 22,55 · 10−6 m3/ mol
Heat of evaporation 293 kJ / mol
Heat of fusion 14.2 kJ / mol
Vapor pressure

2,2 · 10−5Pa at 1323 K

Speed ​​of sound ? m / s
Specific heat capacity 27.2 J / (kg K)
Electric conductivity 0 S / m
Thermal conductivity 12 W / (m K)
Oxidation states 3
Oxides (basicity) (neutral)
Normal potential −2.13 V (Ac3+ + 3e → Ac)
Electronegativity 1.1 (Pauling scale)
isotopeNHt1/2ZMZE MeVZP


2.9 hε1,403224Ra


10 dα5,935221Fr.


29.4 hβ−0,640226Th

< 1="" ·="">−10 %

21,773 aβ−0,045227Th


6.15 h β−2,127228Th
safety instructions
Hazardous substance labeling
R and S phrases R:
further safety information
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Radioactive element
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions.

Actinium (Latinized from Greek ακτίνα, aktína "Beam") is a radioactive chemical element. It is a metal from the group of actinides, which it is named after.

Actinium's chemical behavior is very similar to lanthanum. Actinium is trivalent in all ten known compounds. 26 isotopes are known, of which only two occur naturally. The longest-lived isotope 227 (half-life 21.8 years) is an alpha and beta emitter. Actinium-227 is a decay product of uranium-235 and occurs to a small extent in uranium ores, from which weighable amounts of actinium-227 can be obtained, which thus enable a relatively simple study of this element. Since there are some gamma emitters among the radioactive decay products, complex radiation protection precautions are necessary. The metal is shiny silver-white and relatively soft. It is very reactive and can be attacked by air and water. The Ac (III) ion is colorless.

Extraction and presentation

Since there is little actinium in uranium ores, this source does not play a role in the extraction. Technically, actinium-227 is produced by irradiating radium-226 with neutrons in nuclear reactors. Due to the rapid disintegration of actinium, only small quantities have so far been produced. The first man-made production of actinium was carried out at the Argonne National Laboratory in Chicago.


Actinium is used to generate neutrons, which play a role in activation analyzes. It is also used for thermionic energy conversion.

The decay of Ac-227 is dual: While most of it passes into Th-227 with the emission of beta particles, about 1% decays through alpha emission to Fr-223. A solution of Ac-227 can therefore be used as a source for the short-lived Fr-223. The latter can then be separated and examined regularly.