Periodic Table > Palladium


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 10  Melting point 1554.8°C, 2830.6°F, 1828 K 
Period Boiling point 2963°C, 5365°F, 3236 K 
Block Density (g cm−3) 12.0 
Atomic number 46  Relative atomic mass 106.42  
State at 20°C Solid  Key isotopes 106Pd 
Electron configuration [Kr] 4d10  CAS number 7440-05-3 
ChemSpider ID 22380 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 represents the asteroid Pallas, after which the element is named. In the background are 20th-century star charts.
A shiny, silvery-white metal that resists corrosion.
Most palladium is used in catalytic converters for cars. It is also used in jewellery and some dental fillings and crowns. White gold is an alloy of gold that has been decolourised by alloying with another metal, sometimes palladium.

It is used in the electronics industry in ceramic capacitors, found in laptop computers and mobile phones. These consist of layers of palladium sandwiched between layers of ceramic.

Finely divided palladium is a good catalyst and is used for hydrogenation and dehydrogenation reactions. Hydrogen easily diffuses through heated palladium and this provides a way of separating and purifying the gas.
Biological role
Palladium has no known biological role. It is non-toxic.
Natural abundance
Palladium has been found uncombined in nature, in Brazil, but most is found in sulfide minerals such as braggite. It is extracted commercially as a by-product of nickel refining. It is also extracted as a by-product of copper and zinc refining.

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) 2.10 Covalent radius (Å) 1.30
Electron affinity (kJ mol−1) 54.225 Electronegativity
(Pauling scale)
Ionisation energies
(kJ mol−1)


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.

Supply risk

Relative supply risk 7.6
Crustal abundance (ppm) 0.000037
Recycling rate (%) >30
Substitutability High
Production concentration (%) 60
Reserve distribution (%) 95
Top 3 producers
  • 1) South Africa
  • 2) Russia
  • 3) Zimbabwe
Top 3 reserve holders
  • 1) South Africa
  • 2) Russia
  • 3) USA
Political stability of top producer 44.3
Political stability of top reserve holder 44.3


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 4, 2, 0
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  102Pd 101.906 1.02
  104Pd 103.904 11.14
  105Pd 104.905 22.33
  106Pd 105.903 27.33
  108Pd 107.904 26.46
  110Pd 109.905 11.72


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)
244 Young's modulus (GPa) 46
Shear modulus (GPa) 18 Bulk modulus (GPa) 33
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
- - - 8.27
x 10-9
x 10-5
0.00277 0.144 3.07 30.4 - -
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As early as 1700, miners in Brazil were aware of a metal they called ouro podre, ‘worthless gold,’ which is a native alloy of palladium and gold. However, it was not from this that palladium was first extracted, but from platinum, and this was achieved in 1803 by William Wollaston. He noted that when he dissolved ordinary platinum in aqua regia (nitric acid + hydrochloric acid) not all of it went into solution.

It left a residue from which he eventually extracted palladium. He did not announce his discovery but put the new metal on sale as a ‘new silver’. Richard Chenevix purchased some, investigated it, and declared it to be an alloy of mercury and platinum. In February 1805 Wollaston revealed himself as its discoverer and gave a full and convincing account of the metal and its properties.
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Listen to Palladium Podcast
Transcript :

Chemistry in its element: palladium


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, an element whose discovery was announced in a very unique way. So to explain more above the discovery and chemistry of palladium, here's Simon Cotton.

Simon Cotton

For the first 5 years of my life, I lived in the Norfolk market town that was the birthplace of the discoverer of palladium, William Hyde Wollaston.

When he isolated this metal in 1802, he did something quite unique. Instead of announcing it in a reputable scientific journal, he described its properties in an anonymous leaflet, displayed in the window of a shop in Gerrard Street, Soho, in April 1803.

Entitled 'PALLADIUM; OR, NEW SILVER', this handbill described properties of the new element, giving its density and several of its chemical properties, concluding with the announcement that it was sold only at that shop 'In Samples of Five Shillings, Half a Guinea & One Guinea each.'

No one was able to refute Wollaston's claim for a new element, but it was not until 1805 that he published his discovery in a scientific journal.

Palladium is a remarkable metal, not least because it will absorb over 900 times its volume of hydrogen gas. The hydrogen is released again when the metal is heated, so this can be a rather cunning way of weighing hydrogen. And because palladium won't absorb any other gas, you can use this property to purify hydrogen.

At the bottom of our hearts, we know that the age of cheap energy is over. Quite apart from worries about the greenhouse effect and global warming, oil is running out, and the search is on for green alternatives, and palladium is concerned in the most controversial claim that has been made in this area.

Life on Earth relies on the sun. The sun produces energy by fusing hydrogen atoms together to produce helium, a process that requires extremely high temperatures. On March 23 1989, two scientists working in the USA, Martin Fleischmann and Stanley Pons, reported results of room-temperature electrolysis of heavy water using a platinum anode and a palladium cathode. They claimed to have produced excess energy, and suggested that it arose from nuclear fusion reactions. This was seen as a source of cheap energy, possibly solving the world's energy problems.

When hydrogen molecules first come into contact with palladium, they are adsorbed on the surface, but then they diffuse throughout the metal. In palladium saturated with hydrogen, the molecules are extremely close together. Fleischmann and Pons believed that this closeness had led to the energy-producing nuclear fusion reactions happening. Over the last twenty years, no one has been able to reproduce this, and the reaction has passed into the realms of Voodoo Science.

Palladium does however have a genuine use in 'green' energy, as a catalyst in hydrogen fuel cells. Palladium is one of a number of metals starting to be used in the fuel cells to power a host of things including cars and buses.

Palladium is also widely used in catalytic reactions in industry, such as in hydrogenation of unsaturated hydrocarbons, as well as in jewellery and in dental fillings and crowns.

But the main use of palladium, along with rhodium and platinum, is in the three-way catalytic converters in car exhaust systems. Untreated, car exhaust fumes contain several undesirable gases, and the purpose of the catalytic converters is to eliminate them. They are called three-way converters as they reduce three types of harmful emissions. Converting toxic carbon monoxide into carbon dioxide; the hydrocarbons in unburned fuel into carbon dioxide and water; and toxic oxides of nitrogen (which can contribute to smog and acid rain) into harmless nitrogen gas.

So, that's palladium - a metal with humble beginnings that now plays a major role in industrial catalysis, powering and cleaning up after our vehicles and even makes the occasional appearance in our jewellery boxes, and even in our mouths.

Meera Senthilingam

Quite the catalyst that palladium! Providing energy in fuel cells, protecting our environment through catalytic converters, and providing aesthetic pleasure in jewellery and even dentistry. That was Simon Cotton, from Uppingham School in the UK, with the chemistry of palladium.

Next week, an element that certainly doesn't deserve to be called boring.

Louise Natrajan

There is a famous quote about the lanthanides by Pimentel and Sprately from their book, Understanding Chemistry published in 1971:

'Lanthanum has only one important oxidation state in aqueous solution, the +3 state. With few exceptions, this tells the whole boring story about the other 14 elements.'

If you've listened to any other of the podcasts in the lanthanide series, I hope you'll agree that this is far from true. While, the most common oxidation state of the lanthanides is indeed the +3 valence state, ytterbium, the last and smallest of the lanthanides or rare earths in the series is one of the exceptions Pimentel and Sprately were talking about.

Meera Senthilingam

And Louise Natrajan will be revealing the true - exciting - nature of ytterbium that makes it one of the exceptions, 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

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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

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