Protactinium (Pa)

Protactinium is the 91st element in the periodic table and has a symbol of Pa and atomic number of 91. It has an atomic weight of (231.03588) and a mass number of 231. Protactinium has ninety-one protons and one hundred forty neutrons in its nucleus, and ninety-one electrons in seven shells. It is located in group zero, period seven and block f of the periodic table. Radioactive metallic element, belongs to the actinoids. The most stable isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other radioactive isotopes are known. No practical applications are known. Discovered in 1917 by Lise Meitner and Otto Hahn.

Atomic Number	91
Atomic Weight	231.03588
Mass Number	231

Group
Period	7
Block	f

Protons	91 p⁺
Neutrons	140 n⁰
Electrons	91 e^-

Animated Bohr Model of Pa (Protactinium)

Properties

Physical Properties
Atomic Radius	180 pm 285 pm
Molar Volume	15 cm³/mol
Covalent Radius	169 pm 138 pm 129 pm 200 pm
Metallic Radius
Ionic Radius	104 pm 90 pm 101 pm 78 pm 91 pm 95 pm 119.9 pm
Crystal Radius	118 pm 104 pm 115 pm 92 pm 105 pm 109 pm 133.9 pm
Van der Waals Radius	243 pm 264 pm 342.4 pm
Density	15.4 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy	5.89 eV/particle 11.9 eV/particle 19 eV/particle 30.9 eV/particle 44.3 eV/particle 72 eV/particle 85.1 eV/particle 98.9 eV/particle 111 eV/particle 137 eV/particle 153 eV/particle 187 eV/particle 203 eV/particle 292 eV/particle 316 eV/particle 342 eV/particle 369 eV/particle 395 eV/particle 423 eV/particle 460 eV/particle 488 eV/particle 518 eV/particle 546 eV/particle 690 eV/particle 720 eV/particle 760 eV/particle 790 eV/particle 880 eV/particle 920 eV/particle 1,020 eV/particle 1,060 eV/particle 1,150 eV/particle 1,220 eV/particle 1,300 eV/particle 1,370 eV/particle 1,450 eV/particle 1,520 eV/particle 1,600 eV/particle 1,670 eV/particle 1,760 eV/particle 1,830 eV/particle 1,910 eV/particle 2,000 eV/particle 2,060 eV/particle 2,130 eV/particle 2,483 eV/particle 2,550 eV/particle 2,620 eV/particle 2,696 eV/particle 2,766 eV/particle 2,837 eV/particle 2,968 eV/particle 3,040 eV/particle 3,119 eV/particle 3,193 eV/particle 3,488 eV/particle 3,558 eV/particle 3,637 eV/particle 3,709 eV/particle 4,077 eV/particle 4,161 eV/particle 4,370 eV/particle 4,454 eV/particle 7,181 eV/particle 7,341 eV/particle 7,510 eV/particle 7,690 eV/particle 7,870 eV/particle 8,040 eV/particle 8,410 eV/particle 8,590 eV/particle 8,780 eV/particle 8,960 eV/particle 9,460 eV/particle 9,620 eV/particle 9,790 eV/particle 9,950 eV/particle 11,100 eV/particle 11,280 eV/particle 11,660 eV/particle 11,840 eV/particle 24,660 eV/particle 25,080 eV/particle 25,540 eV/particle 25,970 eV/particle 30,230 eV/particle 30,800 eV/particle 31,520 eV/particle 31,971.6 eV/particle 126,296.6 eV/particle 128,507 eV/particle

Heat of Vaporization	481.2 kJ/mol
Heat of Fusion	16.7 kJ/mol
Heat of Formation	563 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 20, 9, 2

Valence Electrons	2

Electron Configuration	[Rn] 5f² 6d¹ 7s²

Oxidation States	2, 3, 4, 5
Electronegativity	0.12149 1.5
Electrophilicity
Phases
Phase	Solid
Gas Phase
Boiling Point
Melting Point	1,845.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Protactinium is a Silver. Pa has a CPK of #ffffff, Jmol of #00a1ff, and MOLCAS GV of #00a1ff. The Appearance of Element 91 is bright, silvery metallic luster.
Color	Silver #ffffff #00a1ff #00a1ff
Appearance	bright, silvery metallic luster
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	5.6 MS/m
Electrical Resistivity	0.00000018 m Ω
Superconducting Point	1.41 K
Magnetism
Type	paramagnetic
Magnetic Susceptibility (Mass)	0.0000000325 m³/Kg
Magnetic Susceptibility (Molar)	0.000000007509 m³/mol
Magnetic Susceptibility (Volume)	0.0004995
Magnetic Ordering
Curie Point
Neel Point
Structure
The Crystal Structure of Protactinium is TET. The lattice constant of Pa is 3.92 Å. The lattice angles of Element 91 are π/2, π/2, π/2.
Crystal Structure	Centered Tetragonal (TET)
Lattice Constant	3.92 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 Glawe Number of Protactinium is 35. The Mendeleev Number of Pa is 18. The Pettifor Number of Element 91 is 46. The Geochemical Class of Protactinium (Pa) is U/Th decay series. The Goldschmidt Class of Protactinium is litophile.
Category	Actinides, Actinides
CAS Group
IUPAC Group
Glawe Number	35
Mendeleev Number	18
Pettifor Number	46
Geochemical Class	U/Th decay series
Goldschmidt Class	litophile
Other
The Dipole Polarizability of Protactinium is 154 plus or minus 20 a₀. The Allotropes of Pa is . The Neutron Cross Section of Element 91 is 200. The Quantum Numbers of Protactinium (Pa) is 4K11/2. The Space Group of Protactinium is 139 (I4/mmm).
Gas Basicity
Dipole Polarizability	154 ± 20 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section	200
Neutron Mass Absorption
Quantum Numbers	4K11/2
Space Group	139 (I4/mmm)

Isotopes of Protactinium

Stable Isotopes	1
Unstable Isotopes	30
Radioactive Isotopes	31

²¹¹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	211.023674036 ± 0.000074581 Da
Mass Number	211
G-Factor
Half Life	6 ± 3 ms
Spin	9/2
Quadrupole Moment
Discovery Year	2006
Parity	-

²¹¹Pa Decay Modes

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

²¹²Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	212.023184819 ± 0.000094047 Da
Mass Number	212
G-Factor
Half Life	5.8 ± 1.9 ms
Spin	3
Quadrupole Moment
Discovery Year	1997
Parity	+

²¹²Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹³Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	213.021099644 ± 0.000061374 Da
Mass Number	213
G-Factor
Half Life	7.4 ± 2.4 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1995
Parity	-

²¹³Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁴Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	214.020891055 ± 0.00008718 Da
Mass Number	214
G-Factor
Half Life	17 ± 3 ms
Spin	7
Quadrupole Moment
Discovery Year	1995
Parity	+

²¹⁴Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁵Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	215.019113955 ± 0.000088513 Da
Mass Number	215
G-Factor
Half Life	14 ± 2 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1979
Parity	-

²¹⁵Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁶Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	216.019134633 ± 0.000026459 Da
Mass Number	216
G-Factor
Half Life	105 ± 12 ms
Spin	5
Quadrupole Moment
Discovery Year	1972
Parity	+

²¹⁶Pa Decay Modes

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

²¹⁷Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	217.018309024 ± 0.000013417 Da
Mass Number	217
G-Factor
Half Life	3.8 ± 0.2 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1968
Parity	-

²¹⁷Pa Decay Modes

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

²¹⁸Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	218.020021133 ± 0.000019158 Da
Mass Number	218
G-Factor
Half Life	108 ± 5 us
Spin	8
Quadrupole Moment
Discovery Year	1979
Parity	-

²¹⁸Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²¹⁹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	219.019949909 ± 0.000074831 Da
Mass Number	219
G-Factor
Half Life	56 ± 9 ns
Spin	9/2
Quadrupole Moment
Discovery Year	2005
Parity	-

²¹⁹Pa Decay Modes

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

²²⁰Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	220.021769753 ± 0.000015732 Da
Mass Number	220
G-Factor
Half Life	0.85 ± 0.06 us
Spin	1
Quadrupole Moment
Discovery Year	2005
Parity	-

²²⁰Pa Decay Modes

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

²²¹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	221.021873393 ± 0.000063746 Da
Mass Number	221
G-Factor
Half Life	5.9 ± 1.7 us
Spin	9/2
Quadrupole Moment
Discovery Year	1983
Parity	-

²²¹Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²²Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	222.023687064 ± 0.000092975 Da
Mass Number	222
G-Factor
Half Life	3.8 ± 0.2 ms
Spin	1
Quadrupole Moment
Discovery Year	1970
Parity	-

²²²Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²³Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	223.023980414 ± 0.000081193 Da
Mass Number	223
G-Factor
Half Life	5.3 ± 0.3 ms
Spin	9/2
Quadrupole Moment
Discovery Year	1970
Parity	-

²²³Pa Decay Modes

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

²²⁴Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	224.025617286 ± 0.000008145 Da
Mass Number	224
G-Factor
Half Life	844 ± 19 ms
Spin	5
Quadrupole Moment
Discovery Year	1958
Parity	-

²²⁴Pa Decay Modes

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

²²⁵Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	225.026147927 ± 0.000087887 Da
Mass Number	225
G-Factor
Half Life	1.71 ± 0.1 s
Spin	5/2
Quadrupole Moment
Discovery Year	1958
Parity	-

²²⁵Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%

²²⁶Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	226.027948217 ± 0.000012037 Da
Mass Number	226
G-Factor
Half Life	1.8 ± 0.2 m
Spin	1
Quadrupole Moment
Discovery Year	1949
Parity	-

²²⁶Pa Decay Modes

Decay Mode	Intensity
α (α emission)	74%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	26%

²²⁷Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	227.028803586 ± 0.000007797 Da
Mass Number	227
G-Factor
Half Life	38.3 ± 0.3 m
Spin	5/2
Quadrupole Moment
Discovery Year	1948
Parity	-

²²⁷Pa Decay Modes

Decay Mode	Intensity
α (α emission)	85%
ϵ (electron capture)	15%

²²⁸Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	228.031050758 ± 0.000004659 Da
Mass Number	228
G-Factor	1.1666666666667 ± 0.16666666666667
Half Life	22 ± 1 h
Spin	3
Quadrupole Moment
Discovery Year	1948
Parity	+

²²⁸Pa Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	98.15%
α (α emission)	1.85%

²²⁹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	229.032095585 ± 0.000003521 Da
Mass Number	229
G-Factor
Half Life	1.55 ± 0.04 d
Spin	5/2
Quadrupole Moment
Discovery Year	1949
Parity	+

²²⁹Pa Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	99.51%
α (α emission)	0.49%

²³⁰Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	230.034539717 ± 0.000003261 Da
Mass Number	230
G-Factor	1 ± 0.1
Half Life	17.4 ± 0.5 d
Spin	2
Quadrupole Moment
Discovery Year	1948
Parity	-

²³⁰Pa Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	92.2%
β⁻ (β⁻ decay)	7.8%
α (α emission)	0.0032%

²³¹Pa

Abundance	Radioactive ☢️ 100
Relative Atomic Mass	231.0358825 ± 0.000001901 Da
Mass Number	231
G-Factor	1.3266666666667 ± 0.013333333333333
Half Life	32.65 ± 0.2 ky
Spin	3/2
Quadrupole Moment	-1.72 ± 0.05
Discovery Year	1918
Parity	-

²³¹Pa Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	3%
24Ne (heavy cluster emission)	13.4%
23F	9.9%

²³²Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	232.038590205 ± 0.000008206 Da
Mass Number	232
G-Factor
Half Life	1.32 ± 0.02 d
Spin	2
Quadrupole Moment
Discovery Year	1949
Parity	-

²³²Pa Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
ϵ (electron capture)	%

²³³Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	233.040246535 ± 0.000001433 Da
Mass Number	233
G-Factor	2.6666666666667 ± 0.46666666666667
Half Life	26.975 ± 0.013 d
Spin	3/2
Quadrupole Moment	-3 ± 0.4
Discovery Year	1938
Parity	-

²³³Pa Decay Modes

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

²³⁴Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	234.043305555 ± 0.000004395 Da
Mass Number	234
G-Factor
Half Life	6.7 ± 0.05 h
Spin	4
Quadrupole Moment
Discovery Year	1913
Parity	+

²³⁴Pa Decay Modes

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

²³⁵Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	235.045399 ± 0.000015 Da
Mass Number	235
G-Factor
Half Life	24.4 ± 0.2 m
Spin	3/2
Quadrupole Moment
Discovery Year	1950
Parity	-

²³⁵Pa Decay Modes

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

²³⁶Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	236.048668 ± 0.000015 Da
Mass Number	236
G-Factor
Half Life	9.1 ± 0.1 m
Spin	1
Quadrupole Moment
Discovery Year	1963
Parity

²³⁶Pa Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ SF (β⁻-delayed fission)	6%

²³⁷Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	237.051023 ± 0.000014 Da
Mass Number	237
G-Factor
Half Life	8.7 ± 0.2 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1954
Parity	+

²³⁷Pa Decay Modes

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

²³⁸Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	238.054637 ± 0.000017 Da
Mass Number	238
G-Factor
Half Life	2.28 ± 0.09 m
Spin	3
Quadrupole Moment
Discovery Year	1968
Parity	-

²³⁸Pa Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ SF (β⁻-delayed fission)	2.6%

²³⁹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	239.05726 ± 0.00021 Da
Mass Number	239
G-Factor
Half Life	1.8 ± 0.5 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1995
Parity	+

²³⁹Pa Decay Modes

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

²⁴⁰Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	240.061203 ± 0.000215 Da
Mass Number	240
G-Factor
Half Life
Spin	3
Quadrupole Moment
Discovery Year
Parity	+

²⁴⁰Pa Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

²⁴¹Pa

Abundance	Radioactive ☢️
Relative Atomic Mass	241.064134 ± 0.000322 Da
Mass Number	241
G-Factor
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year
Parity	+

²⁴¹Pa Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

History

In 1900, William Crookes isolated protactinium as an intensely radioactive material from uranium Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring in Germany. A more stable isotope of protactinium was discovered in 1917 by Otto Hahn and Lise Meitner at the Kaiser Wilhelm Institute in Berlin. From the Greek protos meaning first

Discoverers	Fredrich Soddy, John Cranston, Otto Hahn, Lise Meitner
Discovery Location	England/France
Discovery Year	1917
Etymology (Name Origin)	Greek: proto and actinium (parent of actinium); it forms actinium when it radioactively decays.
Pronunciation	PRO-tak-tin-eh-em (English)

Protactinium is toxic and highly radioactive

Protactinium is one of the rarest and most expensive naturally occurring elements

Uses

Owing to its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside of scientific research. With the advent of highly sensitive mass spectrometers, an application of ²³¹Pa as a tracer in geology and paleoceanography has become possible. Protactinium-231 combined with the thorium-230 can be used to date marine sediments. It has no significant commercial applications.

Sources

Does not occur in nature. Found among fission products of uranium, thorium, and plutonium.

Abundance
Abundance in Earth's crust	0.0000014 mg/kg
Abundance in Oceans	0.00000000005 mg/L
Abundance in Human Body	0 %
Abundance in Meteor
Abundance in Sun
Abundance in Universe	0 %

Nuclear Screening Constants

Protactinium on ChemicalAid

Australian Educational Vocabulary ID	scot/3563
CAB ID	7539
CAS Registry Number	7440-13-3
ChEBI ID	33386
ChemSpider ID	22387
DSSTOX compound identifier	DTXCID50147878
DSSTox substance ID	DTXSID50225387
Den Store Danske ID	protactinium
ECHA Substance Infocard ID	100.122.906
Elhuyar ZTH ID	030190
Encyclopedia of China ID (Second Edition)	224618
Encyclopædia Britannica Online ID	science/protactinium
Encyclopædia Universalis ID	protactinium
Freebase ID	/m/025s7xw
French Vikidia ID	Protactinium
GND ID	4175981-3
Gran Enciclopèdia Catalana ID	0135204
Great Russian Encyclopedia Online ID	3168919
InChI	InChI=1S/Pa
InChIKey	XLROVYAPLOFLNU-UHFFFAOYSA-N
KBpedia ID	Protactinium
Library of Congress authority ID	sh85107634
MeSH descriptor ID	D011478
NALT ID	3207
Namuwiki ID	프로트악티늄
National Library of Israel J9U ID	987007541390005171
OmegaWiki Defined Meaning	345414
OpenAlex ID	C505015426
PubChem CID	23945
Quora topic ID	Protactinium
Römpp online ID	RD-16-04500
Store norske leksikon ID	protactinium
Treccani ID	protoattinio
UNII	0S6855V29M
USGS Thesaurus ID	1547
WordNet 3.1 Synset ID	14675887-n

Protactinium (Pa)

Properties

Isotopes of Protactinium

211Pa

211Pa Decay Modes

212Pa

212Pa Decay Modes

213Pa

213Pa Decay Modes

214Pa

214Pa Decay Modes

215Pa

215Pa Decay Modes

216Pa

216Pa Decay Modes

217Pa

217Pa Decay Modes

218Pa

218Pa Decay Modes

219Pa

219Pa Decay Modes

220Pa

220Pa Decay Modes

221Pa

221Pa Decay Modes

222Pa

222Pa Decay Modes

223Pa

223Pa Decay Modes

224Pa

224Pa Decay Modes

225Pa

225Pa Decay Modes

226Pa

226Pa Decay Modes

227Pa

227Pa Decay Modes

228Pa

228Pa Decay Modes

229Pa

229Pa Decay Modes

230Pa

230Pa Decay Modes

231Pa

231Pa Decay Modes

232Pa

232Pa Decay Modes

233Pa

233Pa Decay Modes

234Pa

234Pa Decay Modes

235Pa

235Pa Decay Modes

236Pa

236Pa Decay Modes

237Pa

237Pa Decay Modes

238Pa

238Pa Decay Modes

239Pa

239Pa Decay Modes

240Pa

240Pa Decay Modes

241Pa

241Pa Decay Modes