Platinum
Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, gray-white transition metal. Its name is derived from the Spanish term platina, which is literally translated into "little silver".
Identity
- Atomic mass
- 195.085 u
- Category
- Transition metals
- Group
- 10
- Period
- 6
- Block
- d
- Oxidation States
- +2, +4
- Phase (25 °C)
- Solid
- Appearance
- silvery white
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s1 4f14 5d9
- Short configuration
- [Xe] 4f14 5d9 6s1
- Electrons per shell
- 2, 8, 18, 32, 17, 1
- Electronegativity (Pauling)
- 2.28
- Electron affinity
- 205 kJ/mol
- 1st ionization energy
- 870 kJ/mol
- Ionization energies
- 870 · 1791 kJ/mol
Physical properties
- Melting point
- 1768.3 °C (2041 K)
- Boiling point
- 3824.8 °C (4098 K)
- Density
- 21.45 g/cm³
- Molar heat capacity
- 25.9 J/(mol·K)
Chemical behavior of platinum
Platinum has an anomalous electron configuration ([Xe] 4f¹⁴ 5d⁹ 6s¹), with a single electron in the 6s subshell. Its main oxidation states are +2 and +4, forming square-planar and octahedral coordination complexes of great stability. It is a dense, malleable, ductile, grayish-white precious metal belonging to group 10. It is chemically very inert: it resists atmospheric corrosion at any temperature and does not dissolve in simple acids, but it actively dissolves in hot aqua regia forming chloroplatinic acid. It has an extraordinary surface capacity to chemisorb and dissociate molecular hydrogen and oxygen.
Reactivity
3 Pt + 4 HNO₃ + 18 HCl → 3 H₂[PtCl₆] + 4 NO + 8 H₂O
It dissolves in hot aqua regia releasing nitrogen monoxide and generating a reddish-brown solution of hexachloroplatinic(IV) acid.
2 H₂ + O₂ (Pt catalyst) → 2 H₂O
It catalyzes the spontaneous room-temperature recombination of gaseous hydrogen and oxygen without an external flame, with great heat release.
cis-[PtCl₂(NH₃)₂] (cisplatin)
Square-planar complex that covalently binds to cellular DNA by weaving cross-links between adjacent guanines, halting tumor proliferation.
Pt + O₂ (extreme temperature) → PtO₂ (Adams)
When heated with molten sodium nitrate at high temperature it forms platinum dioxide (Adams' catalyst for hydrogenations).
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Cisplatin | cis-[PtCl₂(NH₃)₂] | World-reference anticancer chemotherapy drug for testicular, ovarian and lung tumors |
| Chloroplatinic acid | H₂PtCl₆·6H₂O | Indispensable soluble precursor for preparing supported industrial platinum catalysts and electroplating baths |
| Platinum dioxide | PtO₂ | Adams' catalyst; finely divided brown powder used for selective catalytic hydrogenation in organic synthesis |
| Platinum hexafluoride | PtF₆ | Extremely vigorous oxidizing agent capable of oxidizing molecular oxygen and the noble gas xenon (Bartlett's historic reaction) |
Electron shell distribution
View in the atom builderIsotopes
Natural platinum consists of six isotopes: five stable ones (¹⁹⁴Pt at 32.86%, ¹⁹⁵Pt at 33.78%, ¹⁹⁶Pt at 25.21%, ¹⁹⁸Pt at 7.16% and ¹⁹²Pt at 0.78%) and a primordial alpha-emitting radionuclide with an ultra-extended half-life of 6.5 × 10¹¹ years, platinum-190 (¹⁹⁰Pt, 0.012%). The platinum-195 isotope has a nuclear spin of 1/2, which makes it an excellent active nucleus for the structural study of metal complexes by nuclear magnetic resonance spectroscopy (¹⁹⁵Pt NMR).
Occurrence and production
It is a scarce element in the lithosphere (about 0.005 ppm or 5 ppb). It appears native in alluvial placers as nuggets and grains alloyed with other platinum-group metals and iron, and in sulfide and arsenide minerals such as cooperite (PtS) and sperrylite (PtAs₂). About 75% of world mining production comes from the Merensky Reef of the Bushveld igneous complex in South Africa, along with deposits in Russia (Norilsk), Zimbabwe and Canada. Its refining involves complex hydrometallurgical sequences of dissolution, precipitation and calcination.
History and origin of the name
Pre-Columbian cultures such as the Tolita-Tumaco culture in Ecuador and Colombia had already mastered the sintering of platinum with gold more than two thousand years ago to create pectorals and sacred figures. In Europe it was formally described by the Spanish scientist and naval officer Antonio de Ulloa in 1748, after the French Geodetic Mission in the Viceroyalty of New Granada. The Spaniards disparagingly called it 'platina' (diminutive of 'plata', silver; little-value silver), considering it a nuisance that contaminated the gold washing sites and even throwing it into the rivers to prevent fraud.
Applications and relevance of platinum
Uses of the element
Platinum is the quintessential automotive catalyst: catalytic converters in diesel and gasoline vehicles use it to oxidize unburned hydrocarbons and carbon monoxide into carbon dioxide and water. In the energy transition it is the indispensable anode and cathode catalyst in hydrogen fuel cells (FCEV). It is also used in luxury jewelry for its unalterable white shine, aviation spark plugs and Pt100 resistance thermometers.
Uses of its compounds
In clinical oncology, platinum drugs (cisplatin, carboplatin and oxaliplatin) are essential in chemotherapy treatments to cure or contain multiple types of cancer. Chloroplatinic acid catalyzes industrial silylation in the manufacture of medical silicone elastomers.
Health, safety and environment
Biological role
It has no biological function in any living being. The bulk elemental metal is biologically inert and non-toxic, being used with great safety in permanent medical implants, stimulation electrodes and pacemakers.
Safety
Unlike the inert metal, certain soluble complex platinum salts (such as chloroplatinates) are potent respiratory allergens capable of inducing 'platinosis', a syndrome of occupational asthma, rhinitis and allergic dermatitis in industrial refinery workers. Platinum chemotherapy drugs cause intense side effects such as nephrotoxicity and nausea.
Environment
Microscopic abrasion of car exhaust catalysts releases platinum particles along the world's highways; however, this platinum is mostly in insoluble metallic form with low ecotoxic bioavailability in soils and aquifers.
Frequently asked questions about Platinum
How did pre-Columbian peoples discover platinum metallurgy centuries before Europe?
Goldsmiths of the pre-Columbian La Tolita culture gathered platinum grains from river sands. Since their wood-fired furnaces could not reach the 1,768 °C needed to melt the pure metal, they mixed the platinum powder with gold powder. When heating the mix, the liquid gold enveloped and bonded the platinum grains by hot sintering; by successively forging and annealing the alloy, they crafted jewelry and ceremonial masks fifteen hundred years before European metallurgy.
How is platinum used in some cancer treatments?
Cisplatin is a medicine that contains platinum and is used to treat several types of cancer. Inside cells, it can bind to DNA and make it difficult to copy correctly. This can stop tumor cells from keep multiplying and favor their death. Cisplatin is not suitable for every patient and can cause side effects, so it is administered under medical supervision.
How does the Pt100 temperature probe measure degrees with millimeter precision?
Platinum has an extraordinarily predictable, reproducible and unalterable linear relationship between its electrical resistance and temperature across a range spanning from −200 °C to +850 °C. Pt100 probes incorporate a fine filament or film of pure platinum calibrated to offer exactly 100 ohms of resistance at 0 °C. By measuring the sensor's electrical resistance, industrial thermometers calculate the temperature with accuracies of hundredths of a degree in chemical reactors and laboratories.
Why is platinum jewelry more expensive and prized than white gold?
Platinum is thirty times scarcer than gold in the Earth's crust and has a higher specific weight, which makes a platinum piece feel notably heavier in the hand. In addition, while white gold is an alloy that requires periodic rhodium plating not to yellow, jewelry platinum is used at 95% metallic purity and keeps its original silvery white for life without wearing down when polished.
How does platinum help reduce car pollution?
A catalyst with an interior structure coated in tiny platinum particles is installed in the exhaust pipe of combustion vehicles. When the engine's toxic gases (such as carbon monoxide and unburned hydrocarbons) brush against the hot platinum surface, platinum accelerates their reaction with oxygen, turning them into less harmful water vapor and carbon dioxide before they exit to the outside.
Why is platinum used in some hydrogen fuel cells?
In a fuel cell, hydrogen reacts with oxygen and produces electricity, water and heat. Platinum acts as a catalyst: it facilitates the reactions that release electrons from hydrogen and allow oxygen to form water. It works well at relatively low temperatures, but it is expensive and scarce. That is why research focuses on reducing the amount needed or replacing it with more abundant materials.
What was Neil Bartlett's historic experiment that oxidized xenon with platinum hexafluoride?
Until 1962, textbooks stated flatly that noble gases were completely inert and incapable of forming stable chemical bonds. Chemist Neil Bartlett synthesized platinum hexafluoride (PtF₆), an oxidizing gas so enormously strong that it stripped an electron from molecular oxygen. Reasoning that the noble gas xenon had a similar ionization energy, he mixed both vapors, instantly precipitating a yellow-orange solid: the first noble-gas compound in history (XePtF₆).
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.