Platinum · element 78
Spanish miners once threw it back in the river as a nuisance, now it cleans the exhaust of most cars
Key facts
Platinum is a dense, silvery white metal that almost nothing will react with. It does not tarnish, it is not touched by single acids, and it stays bright in a furnace where silver would melt. Its name comes from the Spanish platina, little silver, a slightly dismissive nickname from colonists in South America who found it mixed with their gold and had no idea what to do with it.
Today it is anything but a nuisance. Platinum sits at the heart of the catalytic converter in petrol and diesel cars, in drugs used to treat several cancers, in hard disk drives, and in some of the most expensive jewellery made.
Where it is found
Platinum is scarce, present in the Earth's crust at only a few parts per billion. About seven in every ten ounces mined comes from one place, the Bushveld igneous complex in South Africa, where ancient magma slowly cooled and concentrated the platinum group metals into thin layers called reefs. Russia's Norilsk deposits are the second largest source, followed by Zimbabwe, Canada and Montana in the United States.
Platinum occurs as native metal grains and in sulfide and arsenide minerals such as cooperite and sperrylite, and ore grades are tiny: a tonne of rock might yield only a few grams. Scrap catalytic converters are the other major source: they are collected worldwide and the platinum recovered, supplying a substantial share of demand.
How it was discovered
People in what is now Ecuador and Colombia were working platinum long before Europeans arrived. Since no fire they could make would melt it, they mixed platinum grains with gold dust and heated them so the gold bound the grains together, producing tiny masks and ornaments.
Spanish colonists in the 1500s encountered the pale grains in river gold and regarded them as an unwanted impurity. Antonio de Ulloa, a Spanish naval officer who travelled with a French scientific expedition to South America in the 1730s and 1740s, described the metal in an account published in 1748, and is often credited as its discoverer. Chemists across Europe soon confirmed it was a new metal that stubbornly resisted melting and dissolving.
What we use it for
The largest use is in catalytic converters, where platinum, with palladium and rhodium, turns carbon monoxide, unburnt fuel and nitrogen oxides into carbon dioxide, water and nitrogen before they leave the exhaust. Platinum is also the catalyst in hydrogen fuel cells and in the industrial oxidation of ammonia to make nitric acid for fertilisers.
Jewellery is the second biggest use. Platinum jewellery is usually 95 per cent pure, compared with 75 per cent for 18 carat gold, and its white colour never fades. In medicine, cisplatin and its relatives carboplatin and oxaliplatin are platinum compounds that stop cancer cells dividing; they were discovered after a researcher noticed bacteria stopped multiplying near platinum electrodes. Platinum-cobalt alloys store data on hard disk platters, platinum-rhodium bushings spin molten glass into glass fibre, and platinum crucibles hold samples in laboratories.
Reading the numbers
Platinum melts at about 1770 °C and boils near 3830 °C, so it stays solid in a glass furnace and survives red heat without oxidising. Its density of 21.45 grams per cubic centimetre makes it a little denser than gold and nearly three times denser than iron; a platinum ring feels noticeably heavier than the same ring in white gold.
Its electron configuration is [Xe] 4f14 5d9 6s1. You might expect 5d8 6s2, but platinum lowers its energy by shifting one electron into the d shell. Either way it has ten outer electrons, placing it in group 10 below nickel and palladium. Its partly filled d orbitals are what make it a superb catalyst: molecules such as hydrogen and oxygen stick to the surface and their bonds are loosened. An electronegativity of 2.28 and a first ionisation energy of 870 kJ/mol are both high for a metal, the quantitative face of its refusal to react.
Safety and the environment
Platinum metal is biologically inert, which is why it can be used in pacemaker leads and dental work. Some soluble platinum salts are another matter: refinery workers exposed to chloroplatinate dust can develop a severe allergy with asthma and skin reactions. Platinum anti-cancer drugs are deliberately toxic to cells and cause side effects that doctors manage carefully.
Mining platinum is energy and water intensive, and catalytic converters shed minute platinum particles onto roads. Against that, the metal is recycled at high rates because it is so valuable, and every converter prevents far more pollution than it causes.
Did you know?
- Platinum is mined at only a fraction of the rate of gold; world mine output is a couple of hundred tonnes a year, compared with several thousand tonnes of gold.
- The anti-cancer drug cisplatin was discovered by accident in the 1960s when bacteria near platinum electrodes stopped dividing.
- Pre-Columbian metalworkers in South America shaped platinum by binding its grains with gold, centuries before any European furnace could melt it.
- The original international prototype metre and kilogram were both made from a platinum-iridium alloy.
- Platinum belongs to a family of six metals, ruthenium, rhodium, palladium, osmium, iridium and platinum, that are found together and share a resistance to corrosion.
- Most platinum jewellery is 950 fine, meaning 95 per cent pure metal, far purer than typical gold jewellery.
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.
Compare Platinum with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Is platinum rarer than gold?
Yes. Far less platinum is mined each year than gold, and it is present in the Earth's crust at lower concentrations. Most of it comes from a single geological formation in South Africa.
Why is platinum sometimes cheaper than gold?
Price depends on demand as well as rarity. Most platinum is used in industry, especially in car exhaust systems, so its price falls when car sales slow. Gold is bought largely as an investment, and that demand has pushed its price above platinum's in recent years.
Does platinum tarnish?
No. Platinum does not react with oxygen, sulfur compounds or moisture at everyday temperatures, so it keeps its white colour indefinitely. It can develop fine scratches, but these are cosmetic and can be polished out.
What does platinum do in a catalytic converter?
It speeds up reactions that turn harmful exhaust gases into less harmful ones. Carbon monoxide and unburnt fuel are converted to carbon dioxide and water, while nitrogen oxides are broken down into nitrogen and oxygen.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Platinum reference article. Spotted an error? Tell us.