PROTACTINIUM

Introduction

Atomic Number: 91
Group: None
Atomic Weight: 231.03588
Period: 7
CAS Number: 7440-13-3

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

The first isotope of element 91 to be discovered was protactinium-234, also known as UX2, a short-lived member of the naturally occurring uranium-238 decay series. It was identified by K. Fajans and O. H. Gohring in 1913 and they named the new element brevium. When the longer-lived isotope protactinium-231 was identified by Hahn and Meitner in 1918, the name protoactinium was adopted as being more consistent with the characteristics of the most abundant isotope. Soddy, Cranson, and Fleck were also active in this work. The name protoactinium was shortened to protactinium in 1949. In 1927, Grosse prepared 2 mg of a white powder, which was shown to be Pa2O5. Later, in 1934, from 0.1 g of pure Pa2O5 he isolated the element by two methods, one of which was by converting the oxide to an iodide and “cracking” it in a high vacuum by an electrically heated filament by the decomposition of protactinium (V) iodide to protactinium and iodine. Protactinium has a bright metallic luster which it retains for some time in air. The element occurs in pitchblende to the extent of about 1 part protactinium-231 to 10 million of ore. Ores from Zaire have about 3 ppm. Protactinium has twenty four isotopes and isomers, the most common of which is protactinium-231 with a half-life of 32,500 years. A number of protactinium compounds are known, some of which are colored. The element is superconductive below 1.4 K. The element is a dangerous toxic material and requires precautions similar to those used when handling plutonium. In 1959 and 1961, it was announced that the Great Britain Atomic Energy Authority extracted by a 12-stage process 125 g of 99.9% protactinium, the world’s only stock of the metal for many years to come. The extraction was made from 60 tons of waste material at a cost of about $500,000. Protactinium is one of the rarest and most expensive naturally occurring elements. 1

Physical Properties

Melting Point:2*  1572 °C = 1845.15 K = 2861.6 °F
Boiling Point:2
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:3  15.4 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration:  *[Rn] 7s2 5f3
Block: f
Highest Occupied Energy Level: 7
Valence Electrons: 2

Quantum Numbers:

n = 5
ℓ = 3
m = -1
ms = +½

Bonding

Electronegativity (Pauling scale):4 1.5
Electropositivity (Pauling scale): 2.5

Ionization Potential   eV 5  kJ/mol  
Ionization Potential   eV 5  kJ/mol  
Ionization Potential   eV 5  kJ/mol  
1 5.89    568.3

Isotopes

Nuclide Mass 6 Half-Life 6 Nuclear Spin 6 Binding Energy
212Pa 212.02320(8) 8(5) ms [5.1(+61-19) ms] 7+# 1,621.29 MeV
213Pa 213.02111(8) 7(3) ms [5.3(+40-16) ms] 9/2-# 1,629.36 MeV
214Pa 214.02092(8) 17(3) ms 1,637.44 MeV
215Pa 215.01919(9) 14(2) ms 9/2-# 1,654.82 MeV
216Pa 216.01911(8) 105(12) ms 1,662.89 MeV
217Pa 217.01832(6) 3.48(9) ms 9/2-# 1,670.96 MeV
218Pa 218.020042(26) 0.113(1) ms 1,669.72 MeV
219Pa 219.01988(6) 53(10) ns 9/2- 1,687.11 MeV
220Pa 220.02188(6) 780(160) ns 1-# 1,685.86 MeV
221Pa 221.02188(6) 4.9(8) μs 9/2- 1,693.94 MeV
222Pa 222.02374(8)# 3.2(3) ms 1,702.01 MeV
223Pa 223.02396(8) 5.1(6) ms 1,710.08 MeV
224Pa 224.025626(17) 844(19) ms 5-# 1,718.15 MeV
225Pa 225.02613(8) 1.7(2) s 5/2-# 1,726.22 MeV
226Pa 226.027948(12) 1.8(2) min 1,734.29 MeV
227Pa 227.028805(8) 38.3(3) min (5/2-) 1,742.36 MeV
228Pa 228.031051(5) 22(1) h 3+ 1,741.12 MeV
229Pa 229.0320968(30) 1.50(5) d (5/2+) 1,749.19 MeV
230Pa 230.034541(4) 17.4(5) d (2-) 1,757.26 MeV
231Pa 231.0358840(24) 3.276(11)E+4 a 3/2- 1,765.33 MeV
232Pa 232.038592(8) 1.31(2) d (2-) 1,773.40 MeV
233Pa 233.0402473(23) 26.975(13) d 3/2- 1,772.16 MeV
234Pa 234.043308(5) 6.70(5) h 4+ 1,780.23 MeV
235Pa 235.04544(5) 24.44(11) min (3/2-) 1,788.30 MeV
236Pa 236.04868(21) 9.1(1) min 1(-) 1,796.37 MeV
237Pa 237.05115(11) 8.7(2) min (1/2+) 1,795.13 MeV
238Pa 238.05450(6) 2.27(9) min (3-)# 1,803.20 MeV
239Pa 239.05726(21)# 1.8(5) h (3/2)(-#) 1,811.27 MeV
240Pa 240.06098(32)# 2# min 1,810.03 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 6

Abundance

Earth - Seawater: 0.00000000005 mg/L 7
Earth -  Crust:  0.0000014 mg/kg = 0.00000000014% 7

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:25.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(8) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.