Palladium · element 46
The metal in your car's exhaust that soaks up hydrogen like a sponge and quietly cleans the air
Key facts
Palladium is one of the six platinum group metals, a silvery-white metal that rarely gets the attention its heavier cousin platinum enjoys. Yet for most of the last thirty years it has been the more useful of the two. Almost every petrol car built since the 1990s carries a few grams of it in the exhaust system, where it converts poisonous carbon monoxide and unburnt fuel into carbon dioxide and water.
Chemists prize palladium for two habits. It absorbs hydrogen gas into its crystal structure in astonishing quantities, and it speeds up a huge range of reactions without being used up. Those two properties have made it a workhorse of both the car industry and the pharmaceutical laboratory.
Where it is found
Palladium is scarce. It makes up only a few parts per billion of the Earth's crust, which puts it in the same rarity bracket as platinum and gold. Most of the world's supply comes from sulfide ores of nickel and copper, with the palladium separated during refining rather than mined for its own sake.
Two regions dominate. The Norilsk deposits in Siberia and the Bushveld complex in South Africa together supply the large majority of newly mined palladium, with smaller amounts from Canada, the United States and Zimbabwe. Because so much comes from so few places, the price swings sharply whenever supply is threatened, and recycling old catalytic converters has become a significant source in its own right.
How it was discovered
The London chemist William Hyde Wollaston found palladium in 1803 while working through the impurities in crude platinum from South America. He dissolved the platinum in a mixture of nitric and hydrochloric acids and found a new metal in what was left behind. He named it after the asteroid Pallas, which astronomers had spotted only a year earlier.
Wollaston announced his discovery in an unusual way. Rather than publishing a paper, he printed anonymous leaflets and offered the new metal for sale through a shop in Soho. A rival chemist declared it a fraud and offered a reward to anyone who could make it artificially. Nobody could, and Wollaston eventually revealed himself as the discoverer.
What we use it for
The single biggest use is the catalytic converter. Inside the honeycomb of a car exhaust, a thin coating of palladium helps oxygen react with carbon monoxide and leftover hydrocarbons at temperatures far lower than would otherwise be needed.
Beyond cars, palladium catalysts are central to modern organic chemistry. Reactions such as the Suzuki and Heck couplings, which join carbon atoms together with great precision, depend on palladium and are used daily in making medicines and agrochemicals. The 2010 Nobel Prize in Chemistry recognised this work. Palladium also appears in dentistry, in electronics as a coating for capacitor plates and connectors, in white gold jewellery, and in membranes that purify hydrogen gas by letting only hydrogen atoms pass through the metal.
Reading the numbers
Palladium melts at about 1555 °C and boils near 2963 °C. That melting point is high enough for it to survive the heat of an exhaust system for years, but it is the lowest of the platinum group metals, which makes palladium a little easier to work than platinum. Its density of about 12 grams per cubic centimetre makes it twelve times denser than water and half again as dense as iron.
Its electron configuration, [Kr] 4d10, is unusual. Palladium is the only element whose ground state fills a d subshell completely while leaving the outer s subshell empty, so its outermost shell holds 18 electrons rather than the expected one or two. That filled shell explains why palladium is so unreactive in air and why it sits in group 10, below nickel and above platinum, sharing their tendency to form compounds in the +2 oxidation state.
Safety and the environment
Palladium metal is not considered toxic and is safe to handle, which is why it can be used in dental fillings and jewellery. Some soluble palladium compounds irritate skin and eyes, and fine palladium dust should not be inhaled. A small number of people develop a contact allergy to palladium, often alongside a nickel allergy.
Environmentally, the main concern is mining. Extracting platinum group metals from sulfide ores uses a great deal of energy and can release sulfur dioxide. On the other hand, palladium in catalytic converters has removed enormous quantities of pollution from city air, and the metal is recycled at high rates because it is so valuable.
Did you know?
- Palladium can absorb several hundred times its own volume of hydrogen gas, swelling slightly as the hydrogen atoms slip between the metal atoms.
- Wollaston kept his discovery anonymous at first and sold the new metal through a Soho shop, prompting a rival chemist to call it a fake.
- Palladium is named after the asteroid Pallas, which in turn is named after the Greek goddess Pallas Athena.
- The controversial cold fusion announcement of 1989 by Fleischmann and Pons was based on palladium electrodes soaked in heavy water.
- For several years around 2020 palladium cost more per gram than gold, driven almost entirely by demand from car makers.
- Palladium is the only element whose ground-state electron configuration has a completely full outer d subshell and an empty outer s subshell.
More in the transition metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 38 transition metals on one page, or browse all 118 elements.
Frequently asked questions
Is palladium more valuable than gold?
It has been at times. Palladium overtook gold in price in 2019 and stayed above it for several years because car makers needed it for catalytic converters and supply was tight. Prices have since fallen back, and the two metals now trade in the same general range, with gold usually ahead.
Why is palladium used in catalytic converters?
Palladium speeds up the reaction between oxygen and the carbon monoxide and unburnt fuel in exhaust gas, turning them into carbon dioxide and water. It does this at exhaust temperatures without being used up, and it resists the heat and corrosion inside an exhaust for the life of the car. It works especially well for petrol engines.
Is palladium magnetic?
Not in the everyday sense. Palladium is paramagnetic, meaning it is very weakly drawn towards a magnetic field, but a fridge magnet will not stick to it. Only iron, nickel, cobalt and a few alloys show the strong attraction most people mean by magnetic.
Where does the name palladium come from?
William Hyde Wollaston named it in 1803 after the asteroid Pallas, discovered in 1802. Naming elements after newly found bodies in the solar system was fashionable at the time; cerium was named after Ceres in the same year and uranium after Uranus a few years earlier.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Palladium reference article. Spotted an error? Tell us.