Some elements exist in several different structural forms, called allotropes. Each allotrope has different physical properties.

For more information on the Visual Elements image see the Uses and properties section below.



A vertical column in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.

A horizontal row in the periodic table. The atomic number of each element increases by one, reading from left to right.

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 (s), principal (p), diffuse (d), and fundamental (f).

Atomic number
The number of protons in an atom.

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

Melting point
The temperature at which the solid–liquid phase change occurs.

Boiling point
The temperature at which the liquid–gas phase change occurs.

The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.

Density (g cm−3)
Density is the mass of a substance that would fill 1 cm3 at room temperature.

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.

Atoms of the same element with different numbers of 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.

Fact box

Group Melting point Unknown 
Period Boiling point Unknown 
Block Density (g cm−3) Unknown 
Atomic number 108  Relative atomic mass [269]  
State at 20°C Solid  Key isotopes 270Hs 
Electron configuration [Rn] 5f146d67s2  CAS number 54037-57-9 
ChemSpider ID - ChemSpider is a free chemical structure database


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.


The description of the element in its natural form.

Biological role

The role of the element in humans, animals and plants.

Natural abundance

Where the element is most commonly found in nature, and how it is sourced commercially.

Uses and properties

Image explanation
The image is inspired by the coat of arms for the German state of Hesse, which gives the element its name.
A highly radioactive metal, of which only a few atoms have ever been made.
At present it is only used in research.
Biological role
Hassium has no known biological role.
Natural abundance
Hassium does not occur naturally and it will probably never be isolated in observable quantities. It is created by bombarding lead with iron atoms
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There are 15 known isotopes of hassium with mass numbers 263 to 277, with isotope-276 having the longest half-life of 1.1 hour. The first attempt to synthesize element 108 took place in 1978 at Russia’s Joint Institute for Nuclear Research (JINR) in Dubna, where a team headed by Yuri Oganessian and Vladimir Utyonkov bombarded radium with calcium and got isotope 270. In 1983, they obtained other isotopes: by bombarding bismuth with manganese they got isotope 263, by bombarding californium with neon they got isotope 270, and by bombarding lead with iron they got isotope 264.

In 1984, at Germany’s Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, a team headed by Peter Armbruster and Gottfried Münzenberg bombarded lead with iron and synthesised isotope 265. Their data which was considered more reliable than that from JINR and so they were allowed to name the element which they did, basing it on Hesse, the state in which the GSI is located.

Atomic radius, non-bonded
Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.

Covalent radius
Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination.

Electron affinity
The energy released when an electron is added to the neutral atom and a negative ion is formed.

Electronegativity (Pauling scale)
The tendency of an atom to attract electrons towards itself, expressed on a relative scale.

First ionisation energy
The minimum energy required to remove an electron from a neutral atom in its ground state.

Atomic data

Atomic radius, non-bonded (Å) Unknown Covalent radius (Å) 1.34
Electron affinity (kJ mol−1) Unknown Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)


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. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.


Atoms of the same element with different numbers of neutrons.

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

Oxidation states and isotopes

Common oxidation states Unknown
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  270Hs 270.135 - 0.3 m  α 


Data for this section been provided by the British Geological Survey.

Relative supply risk

An integrated supply risk index from 1 (very low risk) to 10 (very high risk). This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores.

Crustal abundance (ppm)

The number of atoms of the element per 1 million atoms of the Earth’s crust.

Recycling rate

The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply.


The availability of suitable substitutes for a given commodity.
High = substitution not possible or very difficult.
Medium = substitution is possible but there may be an economic and/or performance impact
Low = substitution is possible with little or no economic and/or performance impact

Production concentration

The percentage of an element produced in the top producing country. The higher the value, the larger risk there is to supply.

Reserve distribution

The percentage of the world reserves located in the country with the largest reserves. The higher the value, the larger risk there is to supply.

Political stability of top producer

A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.

Political stability of top reserve holder

A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.



Specific heat capacity (J kg−1 K−1)

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K.

Young's modulus

A measure of the stiffness of a substance. 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

A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

Bulk modulus

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume.

Vapour pressure

A 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 and temperature data – advanced

Specific heat capacity
(J kg−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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Listen to Hassium Podcast
Transcript :

Chemistry in its element: hassium


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 are going back in time to resolve an identity crisis. Here's Anna Lewcock.

Anna Lewcock

Do you remember the 80s? The leg warmers, the big hair, the shoulder pads? Many fashion crimes were committed and statements made as a generation fought to carve out its identity.

Looking back on those photos a couple of decades down the line, some might wish they hadn't fought so hard. But it's not just rebellious teenagers or disillusioned 40-somethings that suffer identity crises - elements can too.

In 1984, alongside the introduction of the first Apple Mac computers, GCSEs and the discovery of the Aids virus, a team of researchers in Germany managed to synthesise element 108 for the very first time.

Element 108, today known as hassium, is one of the transactinides and it's most stable isotope - hassium-277 - has a half life of around 12 minutes.

By bombarding lead with iron ions in a linear accelerator, a team lead by Peter Armbruster and Gottfried Münzenber at the Heavy Ion Research Laboratory in Darmstadt, Germany, managed to make three atoms of hassium-265, an isotope with the princely half-life of about 2 milliseconds.

There are only a handful of research centres that have the appropriate equipment to make these superheavy elements, and on occasion more than one institution would claim to be the first to have made an element, and therefore claim the right to name it. Unfortunately, this caused a fair amount of arguing and confusion when several elements ended up with more than one name.

Perhaps most controversial were the American suggestion for element 106 - seaborgium - which was initially objected to on the grounds that Glenn Seaborg, the Nobel prize-winning chemist the element was to be named after, was still alive (which is against the rules according to element naming guidelines) - and then there was the Russian proposal of kurchatovium for element 104, named after nuclear physicist Igor Kurchatov, who led the Soviet project to develop an atomic bomb.

To deal with this, Iupac, the international body responsible for naming elements, decided that elements from atomic number 104 onwards would have temporary names to act as place holders while the wrangling over the official names was sorted out.

These temporary names were based on the Latin for the relevant atomic number - so unnilquandium for 104, unnilpentium for 105 and so on. Element 108 was therefore known as unniloctium. The element's German discoverers wanted the new element to be called hassium, after the Latin name for the German state of Hesse, where their research centre was based.

However, after much talk, Iupac in 1994 decided to call element 108 Hahnium, after Nobel-prize winning chemist Otto Hahn. Hahnium had in fact been the American suggestion for element 105 (now known as dubnium - which had itself been a previous suggestion for element 104). I told you it got messy.

But, by 1997 Iupac had changed its mind again, finally deciding to go with hassium for element 108 around the time of the discovery's 13th anniversary.

As we tipped over into the 21st century the first measurements of hassium's chemical properties were finally reported. By this time the discovery was approaching its 18th birthday, and as an unstable element that reinvented itself in next to no time, it proved just as hard to characterise as any teenager.

Any lingering hard feelings over the naming process were put to one side as an international team of researchers from across the globe (including scientists from Russia, Germany and the US) came together to try and figure out what hassium was all about.

By bombarding curium-248 with energetic magnesium-26 ions, the team formed seven hassium atoms, generated as 269Hs and 270Hs. These two isotopes have half lives of around 10 seconds and 4 seconds respectively - long enough for the researchers to get a good look at some of its chemical properties.

Theoretical calculations suggested that hassium should have similar chemical properties to the group 8 elements such as osmium and ruthenium, for example quickly reacting with oxygen to form hassium tetroxide.

When the researchers tested this theory with their seven atoms, they found that they did indeed immediately oxidise to form seven molecules of hassium tetroxide, providing strong evidence that the element has similar properties to osmium, and cementing its position in the periodic table.

So it turns out hassium doesn't have an identity crisis after all - it knew where it would fit all along.

Meera Senthilingam

So elements, like people, like to fit in as well. And hassium it seems has a firm place in the periodic table. That was Chemistry World's Anna Lewcock with the reassuring chemistry of hassium. Now next week, an element whose placing is still in question.

Eric Scerri

Starting in 1969 the chemical properties of lawrencium began to be explored. In the gas phase the element forms a tri-chloride. Studies of its aqueous phase also show that it displays tri-valency. You might think that these experiments and others like it would have settled the precise position of lawrencium in the periodic table but this has not been the case.

Meera Senthilingam

And to find out how the positioning of lawrencium was decided and whether it stayed that way, join UCLA scientist and author Eric Scerri for the last of our chemical elements. But not to worry, after the elements we'll be bringing you the exciting chemistry of compounds in a brand new series of Chemistry in its element. But until next week's finale, thank you for listening, I'm Meera Senthilingam.


Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by There's more information and other episodes of Chemistry in its element on our website at

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Visual Elements images and videos
© Murray Robertson 2011.



W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J.J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions(version 3.0), 2010, National Institute of Standards and Technology, Gaithersburg, MD, accessed December 2014.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.


Uses and properties

John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.


Supply risk data

Derived in part from material provided by the British Geological Survey © NERC.


History text

© John Emsley 2012.



Produced by The Naked Scientists.


Periodic Table of Videos

Created by video journalist Brady Haran working with chemists at The University of Nottingham.
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