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 105  Relative atomic mass [268]  
State at 20°C Solid  Key isotopes 268Db 
Electron configuration [Rn] 5f146d37s2  CAS number 53850-35-4 
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 features a stylised Cyrillic character version of ‘Dubna’, the Russian town after which the element is named. It is set against an abstracted ‘fractal particle’ background.
A highly radioactive metal, of which only a few atoms have ever been made.
At present, it is only used in research.
Biological role
Dubnium has no known biological role.
Natural abundance
Dubnium does not occur naturally. It is a transuranium element created by bombarding californium-249 with nitrogen-15 nuclei.
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In 1968, a team led by Georgy Flerov at the Russian Joint Institute for Nuclear Research (JINR) bombarded americium with neon and made an isotope of element 105. In 1970, a team led by Albert Ghiorso at the American Lawrence Berkeley Laboratory (LBL) bombarded californium with neon and obtained isotope 261. They disputed the claim of the JINR people. The two groups gave it different names. The Russians called it neilsbohrium, while the Americans called it hahnium, both being derived from the names of prominent nuclear scientists.

Eventually, the International Union of Pure and Applied Chemistry (IUPAC) decided it should be called dubnium.

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) 1.49
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
  268Db 268.126 - 1.2 d  fs, EC 


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 Dubnium Podcast
Transcript :

Chemistry in its element: dubnium


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 Senthilingham

This week: warfare, as the US and Russia fight to find new elements. Simon Cotton:

Simon Cotton

In the days of the Cold War, America and Russia rivalled each other in all sorts of ways. Never mind thermonuclear bombs and intercontinental ballistic missiles to deliver them, they competed in putting men and women into space; who could win the most medals in the Olympic Games; and in making new chemical elements. In the case of element 105, the controversy went on for nearly 30 years and was part of the so-called 'Transfermium Wars', when no blood was spilt but a great deal of ink was.

In the Red corner, the Soviet team at the Joint Institute for Nuclear Research at Dubna, near Moscow, led by Georgy Flerov. In the Blue corner, the American team at the University of California at Berkeley, led by Albert Ghiorso.

In 1968, the Soviet team bombarded an americium-243 target with neon-22 and claimed to have made isotopes of mass 260 or 261 of element 105. First round to Russia. Two years later, the Berkeley group reported bombarding californium 249 with nitrogen-15, and claimed they had made an isotope of element 105 of mass 260 with a half life of around 1.5 seconds. They showed its alpha-decay product was element 103, lawrencium. They gave it the name hahnium, after Otto Hahn, who received the 1944 Nobel Prize in Chemistry for the discovery of nuclear fission. Lise Meitner, a collaborator of Hahn, who had predicted fission, did not get even a mention from the Nobel committee, but more on this later. Also in 1970, the Russians reported more results, with more convincing data. They named it nielsbohrium, after the Danish physicist who was awarded the 1922 Nobel Prize for Physics for his researches on atomic structure and radiation.

As time went on, studies from both laboratories continued, and evidence mounted that element 105 resembled niobium and tantalum, being a member of a 6d transition series. In 1986, the Transfermium Working Group was set up to determine firstly, the criteria that must be satisfied for the discovery of a new chemical element to be recognised and secondly to apply these criteria to the discovery of the transfermium elements. For the time being, in view of the conflicting claims, they kicked for touch and proposed a temporary name of unnilpentium (symbol Unp) while they decided who had synthesised and characterised this element. In 1994, they suggested the name joliotium (Jl), after the French physicist Frederic Joliot-Curie, but this did not find acceptance. Finally in 1997, the working group recognised that both Berkeley and Dubna had made 'significant contributions' to the discovery of elements 104 and 105, and said that since the Berkeley contributions were recognised in the names of elements 104 and 106 (rutherfordium and seaborgium), element 105 should be given the name dubnium, symbol Db, after the town the Russian scientists came from.

Although only a few atoms have ever been made, we know a bit about the chemistry of dubnium. We think that its aqua ion adopts the +5 oxidation state, as the dubnium aqua ion is adsorbed onto glass from solution, just like niobium and tantalum above it in Group 5 - but unlike +3 and +4 ions of lanthanide and actinide metals. Attempts to form fluoride complexes in solution suggest that Db resembles niobium more than tantalum. Chemists have also made some chlorides and bromides, though they may possibly have been studying oxyhalides.

Element 105 has had five names in total, being reinvented almost as often as Madonna.

I mentioned earlier that the American team called it hahnium until 1997; well, now it has been rejected, this name can never be used for the name of an element, whereas in 1997 meitnerium was adopted as the name for element 109. That's right, Otto Hahn got a Nobel prize but no element named after him, whereas Lise Meitner, his co-worker, got no Nobel prize, but an element named after her. In the words that William Shakespeare puts into the mouth of a clown in Twelfth Night 'the whirligig of time brings in his revenges'.

Meera Senthilingham

So all is fair in the world of chemistry, kind of. That was Uppingham School's Simon Cotton bringing us the competitive discovery of dubnium. Now, staying with the transactinides, and the much deserved recognition of Lise Meitner; next week, we discover the chemistry of meitnerium.

Nik Kaltsoyannis

Meitnerium and the other transactinide elements do not exist in ature. They are all man made and have been synthesised in only fantastically small quantities, by combining the atoms of two lighter elements. They are all highly radioactive, with very short half lives, severely limiting the practical chemistry that can be performed on them. Indeed, entirely new experimental techniques, collectively known as "atom at a time" methods, have been developed to study these elements. In these experiments we are not working with moles of atoms, or even recognisable fractions of moles, but literally with single atoms.

Meera Senthilingham

And to find out how these techniques can be performed with such precision, join UCL's Nik Kaltsoyannis in next week's chemistry in its element. Until then, I'm Meera Senthilingham and thank you for listening!


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

(End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.



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 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
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

Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.



Produced by The Naked Scientists.


Periodic Table of Videos

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