Periodic Table > Actinium
 

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 1050 oC, 1922 oF, 1323.15 K 
Period Boiling point 3200 oC, 5792 oF, 3473.15 K 
Block Density (kg m-3) 10060 
Atomic number 89  Relative atomic mass 227.028  
State at room temperature Solid  Key isotopes 227Ac 
Electron configuration [Rn] 6d17s2  CAS number 7440-34-8 
ChemSpider ID 22404 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 imagery here utilizes the Greek character “alpha” and metallic “rays” to suggest the name of the element.
Appearance
A radioactive metal first extracted from natural uranium ores but now made from uranium in atomic reactors. It glows in the the dark because its intense radioactivity excites the surrounding air.
Uses
Actinium is a very powerful source of alpha rays, but is rarely used outside research.
Biological role
Actinium has no known biological role. It is toxic due to its radioactivity.
Natural abundance
Actinium occurs naturally in uranium minerals. It is made by the neutron bombardment of the radium isotope Ra-226.
 
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) 2.470 Covalent radius (Å) 2.01
Electron affinity (kJ mol-1) 33.77 Electronegativity
(Pauling scale)
1.100
Ionisation energies
(kJ mol-1)
 
1st
498.829
2nd
1133.702
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 3
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  227Ac 227.028 - 21.77 y  β- 
        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)
27.2 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

This element was discovered in 1899 by André Debierne at Paris. He extracted it from the uranium ore pitchblende (uranium oxide, U3O8) in which it occurs in trace amounts. In 1902, Friedrich Otto Giesel independently extracted it from the same mineral and, unaware it was already known, gave it the named emanium.


Actinium extracted from uranium ores is the isotope actinium-227 which has half-life of 21.7 years. It occurs naturally as one of the sequence of isotopes that originate with the radioactive decay of uranium-235. A tonne of pitchblende contains around 150 mg of actinium.

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Podcasts

Listen to Actinium Podcast
Transcript :

Chemistry in its element - actinium


(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 glowing element that significantly changed the periodic table. 

Richard Corfield 

When I was a little boy my father used to tell a story about a acquaintance of his who kept a lump of rock in his desk. His party trick - after a few drinks - was to draw the curtains, touch the pebble to the forehead of a volunteer, turn out the light and lead the hilarity as the victim's face blazed with a ghostly blue light. Eventually my father's acquaintance died and his executor started to dispose of his possessions. Finding the lump of rock in his desk, and noticing the sourceless dull blue glow that surrounded it he sought advice. Within hours the house had been sealed off and men in white environment suits with tongs and a lead box were relocating the magic pebble to the Atomic Energy Research Establishment at Harwell in Oxfordshire, the secret hub of Britain's nuclear research and development industry from the end of the Second World War to the 1990s. 

The pebble was, of course, pitchblende; the naturally occurring mineral that Pierre and Marie Curie had used as the source of the radioactive elements that they discovered in the closing years of the 19th century. Pitchblende does not just contain actinium (the topic of this podcast), it also contains radium, radon and polonium; the latter, if we are to believe recent news reports, the Russian assassin's toxin of choice. Actinium, like radium and polonium, emits an ethereal blue radiance which contributes to pitchblende's luminescent properties. Although, radium, radon and polonium were observed first, of all the components of pitchblende actinium was the first to be isolated. 

Actinium was discovered by Andre-Louis Debierne, a friend of Marie and Pierre Curie who worked with them on isolating the radioactive elements in pitchblende. Although he published descriptions of the element in 1899 and then again in 1900 there is some doubt as to whether his techniques had actually allowed the element to be properly identified. What is clear however, is that the German chemist Friedrich Oskar Giesel was also investigating actinium and, by 1904, had unambiguously isolated it. Because of the glow that emanated from it he named his new element emanium. Giesel was an admirer and loyal supporter of the Curie's and consequently was not interested in disputing the priority of discovery of a radioactive element that had come out of a lab whose work he admired hugely. Hence when it became clear that Debierne and Giesel were working on the same element Giesel was content to allow the Frenchman's claim to priority stand, and so today the element is still known by the name Debierne gave it - actinium. 

Whoever discovered it, actinium has an important place in the history of chemistry. It was the first of the non-primordial elements to be discovered. Primordial elements are those that have existed in their current state since before the Earth was formed. In other words their half-life is greater than about 108 years. All stable elements are primordial, as are many radioactive elements. Chemically, actinium, which in its native form is a silvery metal, has similar characteristics to that of the other rare earth elements such as lanthanum. 

Actinium has thirty-six isotopes all of which are radioactive. 227Ac, the isotope which comprises all naturally occurring actinium has the longest half-life at 21,773 years. All the remaining radioactive isotopes have half-lives of the less than ten hours, the majority having half-lives of less than a minute. 

227Ac is about a hundred and fifty times as radioactive as radium making a valuable as the neutron source of energy. Although actinium is found in trace of amounts in uranium ore, more commonly it is synthesised in milligram amounts by the neutron irradiation of radium-226 in a nuclear reactor. 

Actinium gives its name to a block of fifteen elements that lie between actinium and lawrencium in the periodic table with atomic numbers 89 through 103. These actinides - or actinoides as they are more correctly known these days - gain their name from the first element in the series, actinium, itself named after the Greek word for ray thus reflecting the element's - already mentioned - visible radioactivity. 

The actinoides were the first major addition to be made to Mendeleev's periodic table. American physicist Glenn T Seaborg was experiencing unexpected difficulty isolating the elements americium and curium during his work with the Manhattan Project during the second world war. 

He found himself wondering if these elements more properly belonged to a different series from the transition metals, which would explain the differing chemical properties of the new elements he was synthesising in the nuclear reactor at Berkeley University in California. 

In 1945, Seaborg formally proposed the actinides and in so doing created the most significant change to the periodic table since Mendeleev's creation of it in 1869. 

Early in his career, Seaborg was a pioneer in the study of nuclear medicine and developed numerous isotopes of elements with important applications in the diagnosis and treatment of diseases, most notably 131Iodine which is used in the treatment of thyroid disease. Actinium also has a role to play in nuclear medicine. 225Ac can be used as the active agent in Targeted Alpha Therapy (TAT) a technique for inhibiting the growth of secondary cancers by direct irradiation with nuclear material, in this case 213Bi derived from 225Ac. 

And so an element discovered in the same mineral - pitchblende - which kick-started the whole science of nuclear chemistry, today stands at the crossroads of one of the most challenging of all medical disciplines - finding a cure for cancer. The irony is that pitchblende inflicted a dreadful toll on those who worked with it in the early years of the study of radioactivity. Marie Curie suffered terrible radiation burns from handling it, and eventually, in later life, contracted radiation-induced aplastic anaemia from which she died. Even today Marie Curie's papers from the summit of her career in the 1890s - including her cookbook - are still considered too dangerous to handle, and are kept in lead-lined boxes 

Meera Senthilingam 

So whilst offering hope for treating the deadly effects of cancer, the element itself had deadly effects on its founders and therefore must be handled with care. That was science writer Richard Corfield with the radio active chemistry of actinium. Now next week we go beyond the actinides. 

Simon Cotton 

When the last member of the actinide series, element 103 or Lawrencium, was discovered, I was at school doing my A levels. The isotope found had a mass of 258 and it didn't hang about for long - it had a half-life of just 3.8 seconds. This was not unexpected as half lives had been getting shorter right along the actinide series. This discovery prompted the scientific community to start asking, are there any elements waiting to be made beyond Lawrencium, and if so, where would they fit in the Periodic Table? 

Meera Senthilingam 

Join Simon Cotton to find out how element 104, Rutherfordium was discovered and how its place in the periodic table was found, 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) 

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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.