Periodic Table > Polonium
 

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 16  Melting point 254 oC, 489.2 oF, 527.15 K 
Period Boiling point 962 oC, 1763.6 oF, 1235.15 K 
Block Density (kg m-3) 9400 
Atomic number 84  Relative atomic mass 208.982  
State at room temperature Solid  Key isotopes 209Po, 210Po 
Electron configuration [Xe] 4f145d106s26p4  CAS number 7440-08-6 
ChemSpider ID 4886482 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
An image based on Luna E-1, the first spacecraft to reach escape velocity and the first to reach the Moon.
Appearance
Marie Curie isolated polonium from the uranium ore, pitchblende, in which it exists in tiny amounts. It is a radioactive metal produced today in gramme quantities from bismuth in nuclear reactors, and used as a source of alpha radiation or as a heat source in space vehicles.
Uses
Polonium is an alpha-emitter, and is used as an alpha-particle source for scientific research in the form of a thin film on a stainless steel disc. It is also used as a heat source in space equipment. It can be mixed or alloyed with beryllium to provide a source of neutrons.
Biological role
Polonium has no known biological role. It is highly toxic due to its radioactivity.
Natural abundance
Polonium is a very rare natural element. It is obtained when natural bismuth, 209Bi, is bombarded by neutrons to give 210Bi, the parent of polonium.
 
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) 1.970 Covalent radius (Å) 1.42
Electron affinity (kJ mol-1) 183.322 Electronegativity
(Pauling scale)
2.000
Ionisation energies
(kJ mol-1)
 
1st
811.827
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, 4, 2
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  209Po 208.982 - 128 y  α 
  210Po 209.983 - 138.4 d  α 
 

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)
- - - - - - - - - - -
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History

Uranium ores contain minute traces of polonium at levels of parts per billion. Despite this, in 1898 Marie Curie and husband Pierre Curie extracted some from pitchblende (uranium oxide, U3O8) after months of painstaking work. The existence of this element had been forecast by the Mendeleev who could see from his periodic table that there might well be the element that followed bismuth and he predicted it would have an atomic weight of 212. The Curies had extracted the isotope polonium-209 and which has a half-life of 103 years.


Before the advent of nuclear reactors, the only source of polonium was uranium ore but that did not prevent its being separated and used in anti-static devices. These relied on the alpha particles that polonium emits to neutralise electric charge.

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Podcasts

Listen to Polonium Podcast
Transcript :

Chemistry in Its Element - Polonium


(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)

 

Chris Smith

 

Hello, this week in Chemistry in its Element the story of a substance that was named to snub Russia, power space probes keeps paper static free and has even been used as a murder weapon in London.   To reveal the secrets of Marie Curie's element, and that's Polonium, here's Johnny Ball

 

Johnny Ball

 

Polonium, (element 84), was discovered in 1898 and named after Poland, the homeland of Marie Curie (Ne Sklodowska) who found it with her husband Pierre Curie. This loyalty was a direct affront to Russia who had dominated Poland for so long. The only way she could become educated whilst a teenager, was by risking imprisonment by the Russians by attending secret underground schools, which had to change locations every couple of days. It was only by escaping to Paris, following her older brother and sister, that she was able to forge a career. She was so poor in the early years in Paris, that she sometimes fainted through lack of food. Still she worked tirelessly.

 

In 1894 she met Pierre, who had made a name for himself in discovering piezoelectricity and was one of her lecturers. They married in July 1895. She wore a black dress as it would be serviceable for her work in the laboratory. They did not exchange rings, but bought each other a bicycle, on which they honeymooned.  

 

X rays had been discovered by Roentgen (Nov 95) and Uranium radiation by Becquerel (Feb 96) in Paris. Working with him (98), Marie coined the phrase "radio activity" and decided to make this here object of study, because no one else was doing it. They realised that radiation was coming from the very atoms and that this was a sign of the atoms breaking up. Only by studying the break up of atoms through radiation, were scientists able to clearly understand how atoms are made up. For this the Curies and Becquerel shared the Nobel Prize for Physics in 1903.
 
The discovery of Polonium (July 98) was no mean task. Pitchbende, a Uranium bearing ore, seemed to be far to radio active than could be accounted for by the Uranium. The couple got the waste ore free, after the Uranium had been removed. They sieved and sorted by hand, ounce by ounce,  through tons of pitchblende before tiny amounts of Polonium were discovered. With the Polonium extracted, there was clearly something far more radio active left behind and soon they had isolated the much more important element Radium (Dec 98), which they so named as it glowed in the dark. 

 

Pierredied in a tragic accident in 1906, which may have been the result of the pain he was in through radiation burns and sickness. (More on this if you wish)  For discovering Polonium and Radium, Marie received the Nobel Prize for Chemistry in 1911, becoming the only woman to receive two such prizes.  

 

Natural Polonium Po - 210, is still very rare and forms no more than 100 ?g per ton of Uranium ores. As well as Po - 210, Isotopes Po -211 - 212 - 214 - 215 - 216 and - 218 all occur in the chains of radio active elements, as they decay to form Lead Pb -208. However, they exist for very little time indeed, Po 212 comes in two forms, one having a half life of 45.1 seconds and the other of 300 nanoseconds (300/1,000,000,000ths of a second).

 

Because it is so rare, Polonium is made by first making Bismuth (also found in pitchblende). Bismuth -209 is found and then artificially changed to Bismuth -210 which then decays to form Polonium -210. 

 

Polonium has a position in the periodic table that could make it a metal, a metalloid or a nonmetal. It is classed as a metal as it's electrical conductivity decreases as it's temperature rises. Because of this property it is used in industry to eliminate dangerous static electricity in making paper or sheet metal.

 

Because of its short half life, it's decay generates considerable heat (141 W per gram of metal). It can be used as a convenient and very light heat source to generate reliable thermoelectric power in space satellites and lunar stations, as no moving parts are involved.   

 

Chris Smith

 

Johnny Ball lifting the lid on the radioactive element polonium discovered by Marie Curie and her husband Pierre.   Next time on Chemistry in its Element we remain radioactive much like the substance itself with earth scientist Ian Farnan.

 

Ian Farnan

 

Anyone familiar with the iconic image of the mushroom cloud understands the tremendous explosive power of a correctly controlled detonation of plutonium.   The energy density is mind-boggling: a sphere of metal 10 cm in diameter and weighing just 8 Kg is enough to produce an explosion at least as big as the one that devastated Nagasaki in 1945.  

 

 

Chris Smith

 

Ian Farnan with what promises to be an explosive edition of Chemistry in its Element next week.   I'm Chris Smith, thank you for listening and see you next time.

 

(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.