Actinium (Ac)

Actinium is the 89th element in the periodic table and has a symbol of Ac and atomic number of 89. It has an atomic weight of (227) and a mass number of 205. Actinium has eighty-nine protons and one hundred sixteen neutrons in its nucleus, and eighty-nine electrons in seven shells. It is located in group three, period seven and block d of the periodic table. 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 Number	89
Atomic Weight	227
Mass Number	205

Group	3
Period	7
Block	d

Protons	89 p⁺
Neutrons	116 n⁰
Electrons	89 e^-

Properties

Physical Properties
Atomic Radius	195 pm 293 pm
Molar Volume	22.54 cm³/mol
Covalent Radius	186 pm 153 pm 140 pm 215 pm
Metallic Radius
Ionic Radius	112 pm 122 pm
Crystal Radius	126 pm 136 pm
Van der Waals Radius	247 pm 308 pm 347.8 pm
Density	10 g/cm³
Energy
Proton Affinity
Electron Affinity	0.35 eV/particle
Ionization Energy	5.380226 eV/particle 11.75 eV/particle 17.431 eV/particle 44.8 eV/particle 55 eV/particle 67 eV/particle 79 eV/particle 98.9 eV/particle 113.9 eV/particle 143.9 eV/particle 161.1 eV/particle 233 eV/particle 255 eV/particle 279 eV/particle 305 eV/particle 330 eV/particle 355 eV/particle 390 eV/particle 416 eV/particle 444 eV/particle 470 eV/particle 610 eV/particle 640 eV/particle 670 eV/particle 710 eV/particle 780 eV/particle 820 eV/particle 920 eV/particle 950 eV/particle 1,030 eV/particle 1,100 eV/particle 1,170 eV/particle 1,240 eV/particle 1,310 eV/particle 1,380 eV/particle 1,460 eV/particle 1,530 eV/particle 1,610 eV/particle 1,680 eV/particle 1,750 eV/particle 1,820 eV/particle 1,900 eV/particle 1,970 eV/particle 2,298 eV/particle 2,362 eV/particle 2,430 eV/particle 2,503 eV/particle 2,572 eV/particle 2,639 eV/particle 2,762 eV/particle 2,833 eV/particle 2,908 eV/particle 2,980 eV/particle 3,264 eV/particle 3,334 eV/particle 3,409 eV/particle 3,479 eV/particle 3,811 eV/particle 3,893 eV/particle 4,093 eV/particle 4,175 eV/particle 6,767 eV/particle 6,923 eV/particle 7,088 eV/particle 7,265 eV/particle 7,430 eV/particle 7,600 eV/particle 7,950 eV/particle 8,120 eV/particle 8,310 eV/particle 8,480 eV/particle 8,970 eV/particle 9,120 eV/particle 9,290 eV/particle 9,440 eV/particle 10,480 eV/particle 10,660 eV/particle 11,030 eV/particle 11,200 eV/particle 23,480 eV/particle 23,890 eV/particle 24,340 eV/particle 24,760 eV/particle 28,610 eV/particle 29,160 eV/particle 29,850 eV/particle 30,293 eV/particle 119,939 eV/particle 122,062.9 eV/particle

Heat of Vaporization	292.9 kJ/mol
Heat of Fusion	10.5 kJ/mol
Heat of Formation	406 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 18, 9, 2

Valence Electrons	2
Electron Configuration	[Rn] 6d¹ 7s²

Oxidation States	2, 3
Electronegativity	0.10033 1.1
Electrophilicity	0.8159546412794374 eV/particle
Phases
Phase	Solid
Gas Phase
Boiling Point	3,473.15 K
Melting Point	1,323.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Actinium is a Silver. Ac has a CPK of #ffffff, Jmol of #70abfa, and MOLCAS GV of #70abfa.
Color	Silver #ffffff #70abfa #70abfa
Appearance
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity	27.2 J/(mol K)
Specific Heat Capacity	0.12 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Type
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point
Neel Point
Structure
The Crystal Structure of Actinium is FCC. The lattice constant of Ac is 5.31 Å. The lattice angles of Element 89 are π/2, π/2, π/2.
Crystal Structure	Face Centered Cubic (FCC)
Lattice Constant	5.31 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties

Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
The CAS Group of Actinium is IIIA. The IUPAC Group of Ac is IIIB. The Glawe Number of Element 89 is 33. The Mendeleev Number of Actinium (Ac) is 14. The Pettifor Number of Actinium is 48. The Geochemical Class of Ac is U/Th decay series. The Goldschmidt Class of Element 89 is synthetic.
Category	Actinides, Actinides
CAS Group	IIIA
IUPAC Group	IIIB
Glawe Number	33
Mendeleev Number	14
Pettifor Number	48
Geochemical Class	U/Th decay series
Goldschmidt Class	synthetic
Other
The Dipole Polarizability of Actinium is 203 plus or minus 12 a₀. The Allotropes of Ac is . The Neutron Cross Section of Element 89 is 880. The Neutron Mass Absorption of Actinium (Ac) is 0.078. The Quantum Numbers of Actinium is 2D3/2. The Space Group of Ac is 225 (Fm_3m).
Gas Basicity
Dipole Polarizability	203 ± 12 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section	880
Neutron Mass Absorption	0.078
Quantum Numbers	2D3/2
Space Group	225 (Fm_3m)

Isotopes of Actinium

Stable Isotopes	0
Unstable Isotopes	33
Radioactive Isotopes	33

²⁰⁵Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	205.015144152 ± 0.000063682 Da
Mass Number	205
G-Factor
Half Life	80 ± 60 ms
Spin	9/2
Quadrupole Moment
Discovery Year	2014
Parity	-

²⁰⁵Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²⁰⁶Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	206.014476477 ± 0.000069874 Da
Mass Number	206
G-Factor
Half Life	25 ± 7 ms
Spin	3
Quadrupole Moment
Discovery Year	1998
Parity	+

²⁰⁶Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²⁰⁷Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	207.011965967 ± 0.000060384 Da
Mass Number	207
G-Factor
Half Life	31 ± 8 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1994
Parity	-

²⁰⁷Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²⁰⁸Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	208.011552251 ± 0.000069225 Da
Mass Number	208
G-Factor
Half Life	97 ± 15 ms
Spin	3
Quadrupole Moment
Discovery Year	1994
Parity	+

²⁰⁸Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²⁰⁹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	209.009495375 ± 0.000059953 Da
Mass Number	209
G-Factor
Half Life	94 ± 10 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²⁰⁹Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁰Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	210.009408625 ± 0.000066782 Da
Mass Number	210
G-Factor
Half Life	350 ± 40 ms
Spin	7
Quadrupole Moment
Discovery Year	1968
Parity	+

²¹⁰Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹¹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	211.007668846 ± 0.000057706 Da
Mass Number	211
G-Factor
Half Life	213 ± 25 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²¹¹Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹²Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	212.007836442 ± 0.000023492 Da
Mass Number	212
G-Factor
Half Life	895 ± 28 ms
Spin	7
Quadrupole Moment
Discovery Year	1968
Parity	+

²¹²Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹³Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	213.006592665 ± 0.000012522 Da
Mass Number	213
G-Factor
Half Life	738 ± 16 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²¹³Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁴Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	214.0069064 ± 0.000014547 Da
Mass Number	214
G-Factor
Half Life	8.2 ± 0.2 s
Spin	5
Quadrupole Moment
Discovery Year	1968
Parity	+

²¹⁴Ac Decay Modes

Decay Mode	Intensity
α (α emission)	93%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	7%

²¹⁵Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	215.006474061 ± 0.000013318 Da
Mass Number	215
G-Factor
Half Life	171 ± 10 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²¹⁵Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	0.09%

²¹⁶Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	216.008749101 ± 0.000009908 Da
Mass Number	216
G-Factor
Half Life	440 ± 16 us
Spin	1
Quadrupole Moment
Discovery Year	1967
Parity	-

²¹⁶Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁷Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	217.009342325 ± 0.000012048 Da
Mass Number	217
G-Factor	0.85111111111111 ± 0.011111111111111
Half Life	69 ± 4 ns
Spin	9/2
Quadrupole Moment
Discovery Year	1972
Parity	-

²¹⁷Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²¹⁸Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	218.01164886 ± 0.000061853 Da
Mass Number	218
G-Factor
Half Life	1 ± 0.04 us
Spin	1
Quadrupole Moment
Discovery Year	1970
Parity	-

²¹⁸Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	219.012420425 ± 0.000055263 Da
Mass Number	219
G-Factor
Half Life	9.4 ± 1 us
Spin	9/2
Quadrupole Moment
Discovery Year	1970
Parity	-

²¹⁹Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁰Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	220.014754527 ± 0.000006579 Da
Mass Number	220
G-Factor
Half Life	26.36 ± 0.19 ms
Spin	3
Quadrupole Moment
Discovery Year	1970
Parity	-

²²⁰Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²¹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	221.015599721 ± 0.000061086 Da
Mass Number	221
G-Factor
Half Life	52 ± 2 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²²¹Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²²Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	222.017844232 ± 0.000005044 Da
Mass Number	222
G-Factor
Half Life	5 ± 0.5 s
Spin	1
Quadrupole Moment
Discovery Year	1949
Parity	-

²²²Ac Decay Modes

Decay Mode	Intensity
α (α emission)	99%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	1%

²²³Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	223.019135982 ± 0.000007457 Da
Mass Number	223
G-Factor
Half Life	2.1 ± 0.05 m
Spin	5/2
Quadrupole Moment
Discovery Year	1948
Parity	-

²²³Ac Decay Modes

Decay Mode	Intensity
α (α emission)	99%
ϵ (electron capture)	%

²²⁴Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	224.021722249 ± 0.000004389 Da
Mass Number	224
G-Factor	0
Half Life	2.78 ± 0.16 h
Spin	0
Quadrupole Moment	0
Discovery Year	1948
Parity	-

²²⁴Ac Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	90.5%
α (α emission)	9.5%
β⁻ (β⁻ decay)	%

²²⁵Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	225.023228601 ± 0.000005107 Da
Mass Number	225
G-Factor
Half Life	9.919 ± 0.0021 d
Spin	3/2
Quadrupole Moment
Discovery Year	1947
Parity	-

²²⁵Ac Decay Modes

Decay Mode	Intensity
α (α emission)	100%
14C	5.3%

²²⁶Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	226.026096999 ± 0.000003327 Da
Mass Number	226
G-Factor
Half Life	29.37 ± 0.12 h
Spin	1
Quadrupole Moment
Discovery Year	1950
Parity	-

²²⁶Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	83%
ϵ (electron capture)	17%
α (α emission)	0.006%

²²⁷Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	227.027750594 ± 0.000002068 Da
Mass Number	227
G-Factor
Half Life	21.772 ± 0.003 y
Spin	3/2
Quadrupole Moment
Discovery Year	1851
Parity	-

²²⁷Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	98.62%
α (α emission)	1.38%

²²⁸Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	228.031019685 ± 0.000002247 Da
Mass Number	228
G-Factor
Half Life	6.15 ± 0.02 h
Spin	3
Quadrupole Moment
Discovery Year	1908
Parity	+

²²⁸Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²²⁹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	229.032947 ± 0.000013 Da
Mass Number	229
G-Factor
Half Life	62.7 ± 0.5 m
Spin	3/2
Quadrupole Moment
Discovery Year	1952
Parity	+

²²⁹Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁰Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	230.036327 ± 0.000017 Da
Mass Number	230
G-Factor
Half Life	122 ± 3 s
Spin	1
Quadrupole Moment
Discovery Year	1973
Parity	+

²³⁰Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ SF (β⁻-delayed fission)	1.2%

²³¹Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	231.038393 ± 0.000014 Da
Mass Number	231
G-Factor
Half Life	7.5 ± 0.1 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1973
Parity	+

²³¹Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³²Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	232.042034 ± 0.000014 Da
Mass Number	232
G-Factor
Half Life	1.98 ± 0.08 m
Spin	1
Quadrupole Moment
Discovery Year	1986
Parity	+

²³²Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³³Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	233.044346 ± 0.000014 Da
Mass Number	233
G-Factor
Half Life	143 ± 10 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1983
Parity	+

²³³Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁴Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	234.048139 ± 0.000015 Da
Mass Number	234
G-Factor
Half Life	45 ± 2 s
Spin	1
Quadrupole Moment
Discovery Year	1986
Parity	+

²³⁴Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁵Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	235.05084 ± 0.000015 Da
Mass Number	235
G-Factor
Half Life	62 ± 4 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	2006
Parity	+

²³⁵Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁶Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	236.054988 ± 0.000041 Da
Mass Number	236
G-Factor
Half Life	4.5 ± 3.6 m
Spin	3
Quadrupole Moment
Discovery Year	2010
Parity	+

²³⁶Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²³⁷Ac

Abundance	Radioactive ☢️
Relative Atomic Mass	237.057993 ± 0.000429 Da
Mass Number	237
G-Factor
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year
Parity	+

²³⁷Ac Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

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

Discoverers	André Debierne
Discovery Location	France
Discovery Year	1899
Etymology (Name Origin)	Greek: akis, aktinos (ray).
Pronunciation	ak-TIN-i-em (English)

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.

Abundance
Abundance in Earth's crust	0.00000000055 mg/kg
Abundance in Oceans
Abundance in Human Body	0 %
Abundance in Meteor
Abundance in Sun	0 %
Abundance in Universe	0 %

Nuclear Screening Constants

Actinium on ChemicalAid

Australian Educational Vocabulary ID	scot/568
BNCF Thesaurus ID	67637
Bibliothèque nationale de France ID	121509422
CAS Registry Number	7440-34-8
ChEBI ID	33337
ChemSpider ID	22404
DSSTOX compound identifier	DTXCID10147879
DSSTox substance ID	DTXSID10225388
Den Store Danske ID	actinium
DrugBank ID	12860
Encyclopedia of China ID (Second Edition)	190793
Encyclopædia Britannica Online ID	science/actinium
Encyclopædia Universalis ID	actinium
Freebase ID	/m/027sjs4
GEMET ID	68
GND ID	4523163-1
Gran Enciclopèdia Catalana ID	0074647
Great Russian Encyclopedia Online ID	1807988
InChI	InChI=1S/Ac
InChIKey	QQINRWTZWGJFDB-UHFFFAOYSA-N
KBpedia ID	Actinium
Library of Congress authority ID	sh85000706
MeSH descriptor ID	D000186
NALT ID	3219
NKCR AUT ID	ph543052
Namuwiki ID	악티늄
National Library of Israel J9U ID	987007293853405171
OmegaWiki Defined Meaning	33
PSH ID	5759
Probes And Drugs ID	PD058409
PubChem CID	23965
Quora topic ID	Actinium
Römpp online ID	RD-01-00659
Store norske leksikon ID	actinium
Treccani ID	attinio
UNII	NIK1K0956U
USGS Thesaurus ID	1385
WordNet 3.1 Synset ID	14651833-n

Actinium (Ac)

Properties

Isotopes of Actinium

205Ac

205Ac Decay Modes

206Ac

206Ac Decay Modes

207Ac

207Ac Decay Modes

208Ac

208Ac Decay Modes

209Ac

209Ac Decay Modes

210Ac

210Ac Decay Modes

211Ac

211Ac Decay Modes

212Ac

212Ac Decay Modes

213Ac

213Ac Decay Modes

214Ac

214Ac Decay Modes

215Ac

215Ac Decay Modes

216Ac

216Ac Decay Modes

217Ac

217Ac Decay Modes

218Ac

218Ac Decay Modes

219Ac

219Ac Decay Modes

220Ac

220Ac Decay Modes

221Ac

221Ac Decay Modes

222Ac

222Ac Decay Modes

223Ac

223Ac Decay Modes

224Ac

224Ac Decay Modes

225Ac

225Ac Decay Modes

226Ac

226Ac Decay Modes

227Ac

227Ac Decay Modes

228Ac

228Ac Decay Modes

229Ac

229Ac Decay Modes

230Ac

230Ac Decay Modes

231Ac

231Ac Decay Modes

232Ac

232Ac Decay Modes

233Ac

233Ac Decay Modes

234Ac

234Ac Decay Modes

235Ac

235Ac Decay Modes

236Ac

236Ac Decay Modes

237Ac

237Ac Decay Modes