Protactinium

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Protactinium Quick Reference

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Notes

Symbol

Pa

Atomic Number

91

Atomic Weight

Rounded

231.0

for regular calculations

Standard

231.03588 ± 0.00002

for precise calculations

Oxidation States

5

more common

4

less common

3

less common

Pauling Electronegativity

1.5

Electron Configuration

Orbital Occupancy

[Rn] 5f2 6d1 7s2

[Rn] represents the closed-shell electron configuration of radon

Orbital Filling Order

[Rn] 7s2 5f2 6d1

[Rn] represents the closed-shell electron configuration of radon

Term Symbol

4K11/2

see expanded configuration ...

Ionization Energies

I (1)

5.89 eV

Density

solid, 25 °C

15.400 g/cm3

Molar Volume

solid, 298 K, 1 atm

15.18 cm3/mol

Melting Point

1843 ± 50 K

Boiling Point

4722 °C

Thermal Conductivity

solid

300 K

46.6 W/(m K)

provisional value

250 K

45.7 W/(m K)

provisional value

10 K

14.0 W/(m K)

provisional value

4.2 K

 6.2 W/(m K)

provisional value

Pyykkö Covalent Radius

single bond

169 pm

double bond

138 pm

triple bond

129 pm

Atomic Radius

161 pm

Enthalpy of Fusion

1 atm

16.7 kJ/mol

Enthalpy of Vaporization

1 atm

481 kJ/mol

Quantity

Protactinium Atomic Structure

Notes

Ionization Energies

I (1)

5.89 eV

Electron Binding Energies

K    (1s)

112601 eV

LI   (2s)

 21105 eV

LII  (2p1/2)

 20314 eV

LIII (2p3/2)

 16733 eV

see all 21 energies ...

Electron Configuration

Orbital Occupancy

[Rn] 5f2 6d1 7s2

[Rn] represents the closed-shell electron configuration of radon

Orbital Filling Order

[Rn] 7s2 5f2 6d1

[Rn] represents the closed-shell electron configuration of radon

Term Symbol

4K11/2

see expanded configuration ...

Fluorescence Yields

ωK

0.970

ωL1

0.164

ωL2

0.495

ωL3

0.434

Coster-Kronig Yields

F12

0.038

F13

0.62 

F23

0.141

Quantity

Protactinium Physical Properties

Notes

Density

solid, 25 °C

15.400 g/cm3

Molar Mass

Rounded

231.0 g/mol

for regular calculations

Standard

231.03588 ± 0.00002 g/mol

for precise calculations

Molar Volume

solid, 298 K, 1 atm

15.18 cm3/mol

Physical Form

shiny metal

Young's Modulus

76.0 GPa

Electrical Resistivity

solid, 273 K

17.7×10-8 Ohm m

Superconducting Transition Temperature

ambient pressure

1.4 K

0 Pa

1.4 K

Isothermal Bulk Modulus

300 K

76 GPa

estimated

Isothermal Compressibility

300 K

0.013 GPa-1

estimated

Quantity

Protactinium Atomic Interaction

Notes

Oxidation States

5

more common

4

less common

3

less common

Pauling Electronegativity

1.5

Allred-Rochow Electronegativity

1.14

Nagle Electronegativity

1.08

Smith Electronegativity

oxidation state: 5

1.6

oxidation state: 4

1.45

Quantity

Protactinium Thermodynamics

Notes

Melting Point

1843 ± 50 K

Boiling Point

4722 °C

Thermal Conductivity

solid

300 K

46.6 W/(m K)

provisional value

250 K

45.7 W/(m K)

provisional value

10 K

14.0 W/(m K)

provisional value

4.2 K

 6.2 W/(m K)

provisional value

Critical Point

14000 K

Enthalpy of Fusion

1 atm

16.7 kJ/mol

Enthalpy of Vaporization

1 atm

481 kJ/mol

Electronic Heat Capacity Coefficient

5.0 mJ/(mol K2)

Debye Temperature

Low Temperature Limit ( 0 K )

185 K

Room Temperature ( 298 K )

262 K

Quantity

Protactinium Identification

Notes

CAS Number

7440-13-3

Quantity

Protactinium Atomic Size

Notes

Atomic Radius

161 pm

Orbital Radius

180.4 pm

Pyykkö Covalent Radius

single bond

169 pm

double bond

138 pm

triple bond

129 pm

Cordero Covalent Radius

200 pm

Shannon-Prewitt Crystal Radius

ion charge: +3, coordination number: 6

118 pm

ion charge: +4

coordination number: 6

104 pm

coordination number: 8

115 pm

ion charge: +5

coordination number: 6

 92 pm

coordination number: 8

105 pm

coordination number: 9

109 pm

Shannon-Prewitt Effective Ionic Radius

ion charge: +3, coordination number: 6

104 pm

ion charge: +4

coordination number: 6

 90 pm

coordination number: 8

101 pm

ion charge: +5

coordination number: 6

 78 pm

coordination number: 8

 91 pm

coordination number: 9

 95 pm

Pauling Empirical Crystal Radius

ion charge: +4

 98 pm

ion charge: +3

112 pm

Slater Atomic-Ionic Radius

180 pm

Quantity

Protactinium Crystal Structure

Notes

Allotropes

allotrope

α-protactinium

symbol

αPa

allotrope

β-protactinium

symbol

βPa

Nearest Neighbor Distance

300 K, 1 atm

321 pm

Atomic Concentration

300 K, 1 atm

4.01×1022 cm-3

Quantity

Protactinium History

Notes

Discovery

shared discovery

date of discovery

1913

discoverer

Kaisimir Fajans

birth

1887

death

1975

discoverer

Oswald Göhring

location of discovery

Karlsruhe, Germany

shared discovery

date of discovery

1917

discoverer

Otto Hahn

birth

March 8, 1879

death

July 28, 1968

discoverer

Lise Meitner

birth

November 7 (or 17), 1878

death

October 27, 1968

location of discovery

Berlin, Germany

shared discovery

date of discovery

1917

discoverer

Frederick Soddy

birth

September 2, 1877

death

September 22, 1956

discoverer

John Arnold Cranston

birth

1891

death

1972

discoverer

Sir Alexander Fleck

birth

1889

death

1968

location of discovery

Glasgow, Scotland

Origin of Element Name

origin

protos

origin description

property—Greek for first

Origin of Element Symbol

symbol: Pa

origin

protactinium

origin description

element name

Formerly Used or Proposed Element Names and Symbols

name

protoactinium

no matching symbol specified

name

brevium

no matching symbol specified

name

ekatantalum

no matching symbol specified

Quantity

Protactinium Abundances

Notes

Earth's Crust

1.4×10-6 ppm

Ocean Water

2×10-19 ppm

Quantity

Protactinium Nomenclature

Notes

Element Names in Other Languages

French

protactinium

German

Protactinium

Italian

protoattinio

Spanish

protactinio

Portuguese

protacnídio

Anions or Anionic Substituent Groups

protactinide

Cations or Cationic Substituent Groups

protactinium

Ligands

protactinido

Heteroatomic Anion

protactinate

'a' Term—Substitutive Nomenclature

protactina

'y' Term—Chains and Rings Nomenclature

protactiny

References    (Click the button next to a value above to see complete citation information for that entry)

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