89
  Ac  
227.000000
Actinium

Name: Actinium
Symbol: Ac
Atomic Number: 89
Atomic Weight: 227.000000
Family: Rare Earth Elements
CAS RN: 7440-34-8
Description: Silvery-white radioactive metal that glows in the dark.
State (25C): Solid
Oxidation states: +3

Molar Volume: 22.54 cm3/mole
Valence Electrons: 6d17s2
Boiling Point:  3473K, 3200C, 5792F
Melting Point:
1323K, 1050C, 1922F
Electrons Energy Level: 2, 8, 18, 32, 18, 9, 2
Isotopes: 31 + None Stable
Heat of Vaporization: unknown
Heat of Fusion: 62 kJ/mol
Density: 10.07 g/cm3 @ 300K
Specific Heat: 0.12 J/gK
Atomic Radius: 1.88
Ionic Radius: 1.119
Electronegativity: 1.1 (Pauling); 1 (Allrod Rochow)
89
Ac
227.0
90
Th
232.0
91
Pa
231.0
92
U
238.0
93
Np
237.0
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)

1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p6d1 7s2

History

Actinium was discovered in 1899 by Andre-Louis Debierne, a French chemist, who separated it from pitchblende.  Friedrich Oskar Giesel independently discovered actinium in 1902.  The chemical behavior of actinium is similar to that of the rare earth lanthanum.

The word actinium comes from the Greek aktis, aktinos, meaning beam or ray.

Actinium is a rare, extremely radioactive metal that glows in the dark.   Eventual priority was given to Debierne's work.

Characteristics

Actinium is a silvery, radioactive, metallic element.  Due to its intense radioactivity, Actinium glows in the dark with a pale blue light.  It is found only in traces in uranium ores as 227Ac, an alpha and beta emitter with a half-life of 21.773 years.  One ton of uranium ore contains about a tenth of a gram of actinium.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10
6s2 6p6 6d1
7s2

Occurrence

Actinium is found in trace amounts in uranium ore, but more commonly is made in milligram amounts by the neutron irradiation of 226Ra in a nuclear reactor. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300C.

Applications

It is about 150 times as radioactive as radium, making it valuable as a neutron source.   Otherwise it has no significant industrial applications.

225Ac is used in medicine to produce 213Bi in a reusable generator or can be used alone as an agent for radio-immunotherapy for Targeted Alpha Therapy (TAT). 225Ac was first produced artifically by the ITU in Germany using a cyclotron and by Dr Graeme Melville at St George Hospital in Sydney using a linac in 2000.

Isotopes

Naturally occurring actinium is composed of 1 radioactive isotope; 227Ac. 36 radioisotopes have been characterized with the most stable being 227Ac with a half-life of 21.772 years, 225Ac with a half-life of 10.0 days, and 226Ac with a half-life of 29.37 hours.  All of the remaining radioactive isotopes have half-lifes that are less than 10 hours and the majority of these have half lifes that are less than 1 minute.  The shortest-lived isotope of actinium is 217Ac which decays through alpha decay and electron capture.  It has a half-life of 69 ns.   Actinium also has 2 meta states.

Purified 227Ac comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.773-year half-life.

The isotopes of actinium range in atomic weight from 206 amu (206Ac) to 236 amu (236Ac).

Samples of actinium quickly decay to thorium and francium.  The element is obtained as an impurity in pitchblende, an ore mined for its uranium content. One-tenth of one gram of actinium can be recovered from 1 ton of pitchblende.

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Isotope Atomic Mass Half-Life
Ac206   22 ms
Ac207   22 ms
Ac208   95 ms
Ac209 209.001 0.10 seconds
Ac210 210.009 0.35 seconds
Ac211 211.008 0.25 seconds
Ac212 212.0078 0.93 seconds
Ac213 213.0066 0.80 seconds
Ac214 214.007 8.2 seconds
Ac215 215.0065 0.17 seconds
Ac216 216.0087 ~0.33 ms
Ac217 217.0093 69 ns
Ac218 218.0116 1.08 us
Ac219 219.0124 11.8 us
Ac220 220.0148 26.4 ms
Ac221 221.0156 52 ms
Ac222 222.0178 5 seconds
Ac223 223.0191 2.10 minutes
Ac224 224.0217 2.78 hours
Ac225 225.0232 10 days
Ac226 226.0261 29.37 hours
Ac227 227.0278 21.773 years
Ac228 228.031 6.15 hours
Ac229 229.0329 62.7 minutes
Ac230 230.036 122 seconds
Ac231 231.039 7.5 minutes
Ac232 232.042 119 seconds
Ac233 233.045 145 seconds
Ac234 234.048 44 seconds
Ac235   ˜ 40 seconds
Ac236   ˜ 2 minutes

Precautions

40px-Skull_and_crossbones.svg.jpg (1420 bytes) 227Ac is extremely radioactive, and in terms of its potential for radiation induced health effects, 227Ac is even more dangerous than plutonium.  Ingesting even small amounts of 227Ac would present a serious health hazard.

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Actinium Data

 

Atomic Structure

  • Atomic Radius: 1.88
  • Atomic Volume: 22.54cm3/mol
  • Covalent Radius: unknown
  • Cross Section (Thermal Neutron Capture) Barns: 515
  • Crystal Structure: Cubic face centered
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p6d1 7s2
  • Electrons per Energy Level: 2, 8, 18, 32, 18, 9, 2
  • Ionic Radius: 1.119
  • Filling Orbital: 6d1
  • Number of Electrons (with no charge): 89
  • Number of Neutrons (most common/stable nuclide): 138
  • Number of Protons: 89
  • Oxidation States: 3
  • Valence Electrons: 6d1 7s2

Chemical Properties

  • Electrochemical Equivalent: 2.82347 g/amp-hr
  • Electron Work Function: unknown
  • Electronegativity: 1.1 (Pauling); 1 (Allrod Rochow)
  • Heat of Fusion: 62 kJ/mol
  • Incompatibilities: N/A
  • Ionization Potential
    • First: 5.17
    • Second: 12.126
  • Valence Electron Potential (-eV): 38.6

Physical Properties

  • Atomic Mass Average: 227.0728
  • Boiling Point: 3473K, 3200C, 5792F
  • Coefficient of Lineal Thermal Expansion/K-1: 14.9E-6
  • Conductivity
    Electrical:
    Thermal: 0.12 W/cmK
  • Density: 10.07 g/cm3 @ 300K
  • Description:
    Silvery-white radioactive metal that glows in the dark.
  • Enthalpy of Atomization: 301 kJ/mole @ 25C
  • Flammablity Class: N/A
  • Freezing Point: see melting point
  • Heat of Vaporization: kJ/mol
  • Melting Point: 1323K, 1050C, 1922F
  • Molar Volume: 22.54 cm3/mole
  • Physical State (at 20C & 1atm): Solid
  • Specific Heat: 0.12 J/gK

Regulatory / Health

  • CAS Number
    • 7440-34-8
  • NFPA 704
    • Health:
    • Fire:
    • Reactivity:
    • Special Hazard: Radioactive<
    • OSHA Permissible Exposure Limit (PEL)
      • No limits set by OSHA
    • OSHA PEL Vacated 1989
      • No limits set by OSHA
    • NIOSH Recommended Exposure Limit (REL)
      • No limits set by NIOSH
    • Levels In Humans:
      Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
      • Blood/mg dm-3: nil
      • Bone/p.p.m: nil
      • Liver/p.p.m: nil
      • Muscle/p.p.m: nil
      • Daily Dietary Intake: nil
      • Total Mass In Avg. 70kg human: nil

    Who / Where / When / How

    • Discoverer: Andr Debierne
    • Discovery Location: Paris France
    • Discovery Year: 1899
    • Name Origin:
      Greek: aktinos (ray).
    • Abundance:
      • Earth's Crust/p.p.m.: N/A
      • Seawater/p.p.m.: nil
      • Atmosphere/p.p.m.: N/A
      • Sun (Relative to H=1E12): N/A
    • Sources:
      Extremely rare, found in all uranium ores. Usually obtained by treating radium with neutrons in a reactor. Total world production probably less than one gram.
    • Uses:
      Used as a source of neutrons and for thermoelectric power. Not commercially available.

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Ionization Energy (eV): 5.17 eV
Estimated Crustal Abundance: 5.510-10 milligrams per kilogram
Estimated Oceanic Abundance:
unknown

Transition Metals
Group 3
(IIIB)
4
(IVB)
5
(VB)
6
(VIB)
7
(VIIB)
8
(VIIIB)
9
(VIIIB)
10 (VIIIB) 11
(IB)
12
(IIB)
Period 4 21
Sc
44.95
22
Ti
47.86
23
V
50.94
24
Cr
51.99
25
Mn
54.93
26
Fe
55.84
27
Co
58.93
28
Ni
58.69
29
Cu
63.54
30
Zn
65.39
Period 5 39
Y
88.90
40
Zr
91.22
41
Nb
92.90
42
Mo
95.94
43
Tc
98.00
44
Ru
101.0
45
Rh
102.9
46
Pd
106.4
47
Ag
107.8
48
Cd
112.4
Period 6 57
La
138.9
72
Hf
178.4
73
Ta
180.9
74
W
183.8
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.0
79
Au
196.9
80
Hg
200.5
Period 7 89
Ac
227.0
104
Rf
261.0
105
Db
262.0
106
Sg
266.0
107
Bh
264.0
108
Hs
269.0
109
Mt
268.0
110
Ds
269.0
111
Rg
272.0
112
Uub
277.0

(Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond