Periodic Table > Neptunium
 

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 644 oC, 1191.2 oF, 917.15 K 
Period Boiling point 3902 oC, 7055.6 oF, 4175.15 K 
Block Density (kg m-3) 20450 
Atomic number 93  Relative atomic mass 237.048  
State at room temperature Solid  Key isotopes 237Np 
Electron configuration [Rn] 5f46d17s2  CAS number 7439-99-8 
ChemSpider ID 22375 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 symbol used is a representation of the Roman god Neptune’s trident.
Appearance
An artificially made radioactive metal that is extracted in kilogramme quantities from spent uranium rods from nuclear reactors.
Uses
Neptunium is little used outside research.
Biological role
Neptunium has no known biological role. It is toxic due to its radioactivity.
Natural abundance
Neptunium is obtained as a by-product from nuclear reactors. Trace quantities occur naturally in uranium ores.
 
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) 2.390 Covalent radius (Å) 1.8
Electron affinity (kJ mol-1) Unknown Electronegativity
(Pauling scale)
1.300
Ionisation energies
(kJ mol-1)
 
1st
604.548
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 6, 5, 4, 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  236Np 236.047 - 1.55 x 105 EC 
        β- 
  237Np 237.048 - 2.14 x 106 α 
        1 x 1018 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)
- - - - 3.31
x 10-9
1.63
x 10-6
1.68
x 10-4
6.04
x 10-3
0.11 1.06 7.28
  Help text not available for this section currently

History

In early 1934, Enrico Fermi in Italy tried to produce elements 93 and 94 by bombarding uranium with neutrons, and claimed success. Ida Tacke-Noddack questioned Fermi’s claim, pointing out he had failed to do a complete analysis, and all that he had found were fission products of uranium. (Fermi had in fact discovered nuclear fission but not realised it.) In 1938, Horia Hulubei and Yvette Cauchois claimed to have discovered element 93, but the claim was also criticised on the grounds that element 93 did not occur naturally.


Neptunium was first made in 1940 by Edwin McMillan and Philip Abelson at Berkeley, California. It came from a uranium target that had been bombarded with slow neutrons and which then emitted unusual beta-rays indicating a new isotope. Abelson proved there was indeed a new element present.

  Help text not available for this section currently

Podcasts

Listen to Neptunium Podcast
Transcript :

Chemistry in its element - neptunium


(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, a planetary element that helped create the atomic bomb. 

Brian Clegg 

We're so familiar with uranium and plutonium that it's easy to miss that they are named after the seventh and ninth planets of the solar system. (At least, Pluto was the ninth planet until it was stripped of its status in 2006.) Between those planets sits Neptune, and the gap between the two elements leaves a space for their relatively unsung cousin, neptunium - element number 93 in the periodic table. 

In June 1940, American physicists Edwin McMillan and Philip Abelson, working at the Berkeley Radiation Laboratory, wrote a paper describing a reaction of uranium that had been discovered when bombarding it with neutrons using a cyclotron particle accelerator. Remarkably, the openly published Berkeley paper would show the first step to overcoming one of the biggest obstacles to building an atomic bomb - a paper published when both sides in the Second World War were searching for a solution to the uranium problem. 

The trouble with uranium was that the isotope uranium 235 needed to build a bomb was incredibly difficult to separate from the much less rare uranium 238. They are chemically identical. But if uranium 238 can be encouraged to absorb a slow neutron in a reactor, it becomes the unstable isotope uranium 239. This undergoes the nuclear reaction called beta decay, where a neutron turns into a proton, giving off an electron in the process (for historical reasons, the electron is called a beta particle in such circumstances). 

The result of McMillan and Abelson's reaction was the production of a new element, one that had never been seen in nature. By the following year, this element was being called neptunium. But neptunium 239 is also unstable and soon generates another electron, adding a second proton to the nucleus to become plutonium. This was the material that would be used to build the world's first atomic bomb. 

For our purposes, though, the important thing here is that neptunium had been called into existence. It was third time lucky for using this name for an element. In 1877 a German chemist named Hermann had found what he believed was a new element in the mineral tantalite and called it neptunium. Then in 1886, another German, Clemens Winkler, had isolated what we now call germanium and intended to call this neptunium until he discovered Hermann had used the name first. But Hermann's claim was later proved to be a mistake and the neptunium was free again, ready for McMillan and Abelson to deploy. 

The real neptunium sits between uranium and plutonium in the actinides, the floating bar on the periodic table that pops out from between radium and lawrencium. A silvery, metallic substance like so many of its neighbours, its most stable form is the isotope neptunium 237 with a half life - the time it takes for half of the original amount to decay - of over 2 million years, and this is the type of neptunium most likely now to be produced as a by product from nuclear reactors. In the original reaction, though, it was neptunium 239 with a half life of just over 2 days that was formed. 

Although it wasn't spotted until it had already been made in reactors, neptunium does actually exist in a natural form on the earth, when uranium undergoes the process that takes place in a reactor, capturing a neutron from another uranium atom that has split, and emitting a beta particle to transmute it to neptunium - but this only happens in the tiniest quantities. There's much more neptunium to be found in the average household. 

That's because many smoke detectors use alpha particles from the element americium 241 to ionize the air in a detection chamber. The americium gradually converts to neptunium as it decays, though thanks to americium's 432 year half life, there won't be much produced in the lifetime of a detector. 

In practice there is very little use for neptunium. The only significant application is in monitors for high energy neutrons, and even here it is rare. In principle, though, it could have a more deadly use. Where the neptunium 239 produced in 1940 was too unstable to use, quickly transforming into plutonium, Neptunium 237 would be just fine to make an atomic bomb. 

Get enough neptunium 237 together and you've got a nuclear device. The necessary amount to go critical and produce a nuclear explosion is about 60 kilograms. This isn't an impractical quantity. Over 50 tonnes of neptunium is produced as waste from nuclear reactors each year. But neptunium has no particular advantage over plutonium or enriched uranium, so has not been deployed. Even so, because of the risk of it falling into the hands of terrorists or rogue states, neptunium waste has to be treated with the same level of security as the traditional ingredients of atomic bombs. 

In the end, Neptunium has not proved to be the most useful of elements. When it turns up in a nuclear reactor, or as the end product of the decay of americium in smoke detectors, it is regarded as waste, and it's a particularly long lasting, nasty waste with its immense 2 million year half life. But at least neptunium fans can say that it has a name that trumps even New York. Because neptunium was so good they named it thrice. 

Meera Senthilingam 

And so good that it can produce nuclear explosions. That was Brian Clegg with the explosive and long lasting chemistry of neptunium. Now next week an element that likes to avoid the limelight for itself but helps others to get there instead. 

Simon Cotton 

There are lots of everyday applications for yttrium compounds. In its compounds yttrium is always present as the yttrium three plus ion, which means that it is colourless and has no unpaired electrons; therefore it does not have any interesting magnetic or spectroscopic properties of its own. The up side of this is that yttrium compounds make very good host materials for other lanthanides. The most familiar application lies in the red phosphor in cathode ray tubes, as used in traditional colour TV sets. 

Meera Senthilingam 

And Simon Cotton will be revealing more of the supporting roles of yttrium in next week's Chemistry in its Element. Until then I'm Meera Senthilingam and thank you for listening. 

(Promo)

 Chemistry in its element is 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) 

  Help text not available for this section currently
  Help Text

Resources

Description :
The history and background of the Nobel prizes.
Description :
This material introduces 5 Commerical Skills Modules for Chemists developed by KKI Associates and the School of Chemistry at the University of Edinburgh. This resource and its components are licensed...
Description :
Can students spot the potential value in each of 5 potential chemistry-based projects? This resource and its components are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 ...
Description :
Can students estimate the potential time and the likely milestones of 2 out of the 5 chemistry-based projects? This resource and its components are licensed under a Creative Commons Attribution-NonCo...
Description :
Students are asked to summarise and critique 2 out of the 5 chemistry-based projects, based on their previous work, and present their preferred option to a "business" audience. This resource and its ...
Description :
Can students identify and quantify users/customers who receive benefits from 2 out of the 5 chemistry-based projects? This resource and its components are licensed under a Creative Commons Attributio...
 

Terms & Conditions


Images © Murray Robertson 1999-2011
Text © The Royal Society of Chemistry 1999-2011

Welcome to "A Visual Interpretation of The Table of Elements", the most striking version of the periodic table on the web. This Site has been carefully prepared for your visit, and we ask you to honour and agree to the following terms and conditions when using this Site.


Copyright of and ownership in the Images reside with Murray Robertson. The RSC has been granted the sole and exclusive right and licence to produce, publish and further license the Images.


The RSC maintains this Site for your information, education, communication, and personal entertainment. You may browse, download or print out one copy of the material displayed on the Site for your personal, non-commercial, non-public use, but you must retain all copyright and other proprietary notices contained on the materials. You may not further copy, alter, distribute or otherwise use any of the materials from this Site without the advance, written consent of the RSC. The images may not be posted on any website, shared in any disc library, image storage mechanism, network system or similar arrangement. Pornographic, defamatory, libellous, scandalous, fraudulent, immoral, infringing or otherwise unlawful use of the Images is, of course, prohibited.


If you wish to use the Images in a manner not permitted by these terms and conditions please contact the Publishing Services Department by email. If you are in any doubt, please ask.


Commercial use of the Images will be charged at a rate based on the particular use, prices on application. In such cases we would ask you to sign a Visual Elements licence agreement, tailored to the specific use you propose.


The RSC makes no representations whatsoever about the suitability of the information contained in the documents and related graphics published on this Site for any purpose. All such documents and related graphics are provided "as is" without any representation or endorsement made and warranty of any kind, whether expressed or implied, including but not limited to the implied warranties of fitness for a particular purpose, non-infringement, compatibility, security and accuracy.


In no event shall the RSC be liable for any damages including, without limitation, indirect or consequential damages, or any damages whatsoever arising from use or loss of use, data or profits, whether in action of contract, negligence or other tortious action, arising out of or in connection with the use of the material available from this Site. Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise.


We hope that you enjoy your visit to this Site. We welcome your feedback.

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.