Periodic Table > Protactinium
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses/Interesting Facts below.

 

Fact Box Terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact Box

 
Group Actinides  Melting point 1572 oC, 2861.6 oF, 1845.15 K 
Period Boiling point Unknown 
Block Density (kg m-3) 15370 
Atomic number 91  Relative atomic mass 231.036  
State at room temperature Solid  Key isotopes 231Pa 
Electron configuration [Rn] 5f26d17s2  CAS number 7440-13-3 
ChemSpider ID 22387 ChemSpider is a free chemical structure database
 

Interesting Facts terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses / Interesting Facts

 
Image explanation
The image utilizes the Japanese monogram for 'ichi' - number one, reflecting the origin of the element’s name.
Appearance
A radioactive metal, small amounts of which are found naturally in uranium ores. It is also extracted in gramme amounts from spent fuel rods from nuclear reactors.
Uses
Protactinium is little used.
Biological role
Protactinium has no known biological role. It is toxic due to its radioactivity.
Natural abundance
Protactinium is found naturally in uranium ores and produced in gram quantities from uranium fuel elements.
 
Atomic Data Terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic Data

 
Atomic radius, non-bonded (Å) 2.430 Covalent radius (Å) 1.84
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
1.500
Ionisation energies
(kJ mol-1)
 
1st
568.298
2nd
-
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply Risk

 
Scarcity factor Unknown
Country with largest reserve base Unknown
Crustal abundance (ppm) Unknown
Leading producer Unknown
Reserve base distribution (%) Unknown
Production concentration (%) Unknown
Total governance factor(production) Unknown
Top 3 countries (mined)
  • Unknown
Top 3 countries (production)
  • Unknown
 

Oxidation states/ Isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation States / Isotopes

 
Common oxidation states 5, 4
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  231Pa 231.036 100 3.25 x 104 α 
        > 2 x 1017 sf 
 

Pressure and Temperature - Advanced Terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, it provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.

Pressure / Temperature - Advanced

 
Molar heat capacity
(J mol-1 K-1)
Unknown Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) Unknown
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - - - - 3.44
x 10-10
8.06
x 10-8
5.57
x 10-6
1.74
x 10-4
3.06
x 10-3
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History

Mendeleev said there should be an element between thorium and uranium, but it evaded detection. Then, in 1900, William Crookes separated an intensely radioactive material from uranium, but did not identify it. In 1913, Kasimir Fajans and Otto Göhring showed that this new element decayed by beta-emission and it existed only fleetingly. We now know it is a member of the sequence of elements through which uranium decays. It was the isotope protactinium-234, which has a half-life of 6 hours 42 minutes.


A longer-lived isotope was separated from the uranium ore pitchblende (uranium oxide, U3O8) in 1918 by Lise Meitner at the Kaiser-Wilhelm Institute in Berlin. This was the longer-lived isotope protactinium-231, also coming from uranium, and its half-life is 32,500 years.


In 1934, Aristid von Grosse reduced protactinium oxide to protactinium metal by decomposing its iodide (PaF5) on a heated filament.

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Podcasts

Listen to Protactinium Podcast
Transcript :

Chemistry in its element - protactinium


  (Promo)

 

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry

(End promo)

 

Meera Senthilingam

 

This week we've got an element whose origin and location in the periodic table seems to be causing some complications.   To tell us more about the mysteries of Protactinium here's Eric Scerri

 

Eric Scerri 

 

In 1871 the discoverer of the periodic table, Dimitri Mendeleev, made the

following prediction among several others.   I quote:

 

"Between thorium and uranium we can further expect an

element with an atomic weight of about 235. This element should form a

highest oxide X2O5, like niobium and tantalum to which it should be analogous."

 

             The modern atomic weight for the predicted element, or protactinium as it

is now known, is close to 231.  Even though this seems reasonably

accurate, Mendeleev was somewhat unlucky regarding this atomic weight

since he was not to know that protactinium is a member of only four 'pair

reversals' in the entire periodic table.  This situation occurs when two

elements need to be reversed contrary to their atomic weights in order to

order them correctly.  

 

             When atomic number was discovered it turned out to be a better ordering principle than atomic weight for the elements in the periodic table.   All four known pair reversals, including the one concerning protactinium and thorium were suddenly resolved.  Even though protactinium has a lower atomic weight than thorium it should be placed after thorium because of its greater atomic number.

 

             But it appears that Mendeleev's brief predictions were broadly fulfilled

since the element does indeed show an analogy with tantalum in forming

Pa2O5 as its highest and most stable oxide.  Nevertheless protactinium

also shows a strong horizontal analogy with thorium and uranium in also

displaying the +4 oxidation state, something that Mendeleev does not seem

to have anticipated.  Finally, as Mendeleev also correctly predicted

protactinium occurs with uranium, and more specifically in the ore called pitchblende.

 

             But whereas uranium and thorium were isolated in 1789 and 1828

respectively, it was not until the twentieth century before protactinium,

was first discovered.   Of course it depends on what one really means by the discovery of an element.  Does it mean somebody realizing that a mineral contains a new element, or does it mean the first time an element is actually isolated?  Depending on what choice is made the discovery of protactinium can be assigned to different scientists.  And in the case of protactinium there is an even further complication.

 

             In the year 1900 the English scientist and inventor Sir William Crookes

pointed out that a new radioactive substance was present in some ores of

uranium and he called this substance uranium-X.  Uranium-X turned out to

be two different substances later called UX-1 and UX-2 of which the second,

UX-2 was first isolated by the Polish chemist Kasimir Fajans in 1913. 

This was a very short-lived isotope of 234Pa with a half-life of just

over one minute.  Fajans called the new element brevium after its short

half-life.

 

             In 1917 the German physicist Lise Meitner isolated a more stable

isotope of the element, 231Pa with a vastly longer half-life of about 33,000 years. At this point Fajans withdrew the name brevium since the custom was to name

an element according to longest-lived isotope.  Meitner than chose the

somewhat awkward sounding name of protoactinium which was eventually

abbreviated to protactinium.  The name she chose refers to the fact that

this element is the progenitor of element 89 or actinium, which is formed

when protactinium decays via the loss of an alpha particle.  

 

             In the very same year, the same isotope, 231Pa, was independently isolated by Frederick Soddy, who had first coined the term isotope, and his colleague John Cranston when they were working together in Glasgow.

 

             Protactinium is a highly radioactive and highly toxic element with yet no

commercial applications but nevertheless of some scientific interest. 

For example, a measurement of the ratio of 231Pa and 230Th in ocean

sediments allows scientists to reconstruct the movements of bodies of

North Atlanticwater that took place during the melting of the last ice-age.

 

             In 1961 the Atomic Energy Authority in Britain produced a concentrated

mass of 125 grams of protactinium after processing 60 tons of radioactive

waste.  For many years this has remained as the only significant supply

of protactinium which has provided samples of the element to labs around the world.

            

 

Meera Senthilingam

 

So a highly radio active and toxic element whose origin and isolation had scientists mystified.   That was Eric Scerri from the University of California, Los Angeles, with the perplexing tale of protactinium.   Now next week an element that's definitely got one up on the rest when it comes to history. 

 

Brian Clegg

 

Perhaps iridium's best-known claim to fame is as a clue in a piece of a 65 million-year-old Crime Scene Investigation. The concentration of iridium in meteorites is considerably higher than in rocks on the Earth. One class of meteorite, called chondritic (meaning they have a granular structure) still has the original levels of iridium that were present when the solar system was formed.

 

Meera Senthilingam

 

And join Brian Clegg to find out how Iridium can inform us about life on earth in next week's Chemistry in its Element.   Until then I'm Meera Senthilingam and thank you for listening. 

 

 (Promo)

 

Chemistry in its elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

 

(End promo)

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References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.