Pt · Element 78 · Transition metal
The catalyst metal: platinum makes reactions happen that would otherwise need impossible conditions.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where platinum sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All platinum atoms have the same number of protons, 78, and differ only in their number of neutrons: those variants are its isotopes. The most common, Pt-195, has 117 neutrons and makes up 33.775% of natural platinum.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Pt-190 | 112 | 0.012% | 4.97 × 10¹¹ yrs | α |
| Pt-192 | 114 | 0.782% | Stable | — |
| Pt-194 | 116 | 32.864% | Stable | — |
| Pt-195 most common | 117 | 33.775% | Stable | — |
| Pt-196 | 118 | 25.211% | Stable | — |
| Pt-198 | 120 | 7.356% | Stable | — |
Here the classroom shortcut, rounded atomic mass (195.084) minus atomic number, gives the same answer: 117.
Decay modes
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
Radius 139 pm — that is 0.139 nm, so about 3.6 million of them side by side would span a millimetre.
Thermal range
Platinum is liquid over a 2057 K window, from 2041 K to 4098 K.
The story
Platinum (Pt) is element 78, a dense, silvery-white precious metal in group 10 and one of the six platinum group metals. It melts at 1,768 °C (2,041.4 K) and has a density of 21.45 g/cm³, which makes it one of the densest elements. Platinum does not tarnish, resists most acids (it dissolves in hot aqua regia) and is an excellent catalyst.
Platinum has 78 electrons in six shells, arranged 2, 8, 18, 32, 17, 1, with the configuration [Xe] 4f¹⁴ 5d⁹ 6s¹. Its common oxidation states are +2 and +4.
Natural platinum has six isotopes. The most abundant are platinum-195 (about 34%) and platinum-194 (about 33%). Platinum-190 is radioactive but has a half-life of about 500 billion years.
Metalworkers of the La Tolita culture, on the Pacific coast of present-day Ecuador and Colombia, made small objects from platinum and gold alloys centuries before Europeans knew of the metal.
The Spanish naval officer and scientist Antonio de Ulloa encountered the metal in 1735 in the gold-mining region of New Granada (present-day Colombia), during a French and Spanish scientific expedition, and described it in 1748. The Spanish called it platina, "little silver", and miners discarded it as a nuisance in gold ore.
Samples reached England through Charles Wood, and William Brownrigg described them to the Royal Society in 1750. Over the following decades chemists in Sweden, France and England established that platinum was a new metal. Around 1800 William Hyde Wollaston developed a way to make platinum malleable, and in the process he found palladium and rhodium.
Applications
The largest single use of platinum is in vehicle catalytic converters, especially for diesel engines, where it helps convert carbon monoxide, unburned fuel and nitrogen oxides into less harmful gases.
Jewelry is another major use, with demand concentrated in China, Japan, India and the United States. Platinum is also bought as bars and coins.
Where it comes from
0.005 mg/kg of Earth's crust · more abundant than 37% of elements
Platinum is very rare, at about 0.005 parts per million of Earth's crust. It occurs as native platinum, often alloyed with other platinum group metals, and in minerals such as sperrylite (platinum arsenide) and cooperite (platinum sulfide).
Most platinum comes from layered igneous intrusions in which the platinum group metals concentrated in thin reefs, above all the Bushveld Complex in South Africa and the Great Dyke in Zimbabwe. Russia produces platinum as a byproduct of nickel mining at Norilsk, and smaller amounts come from Canada and the United States. Platinum is also found in river gravels, such as those of the Chocó region of Colombia.
According to the USGS, South Africa supplies about 70% of mined platinum. A growing share of supply comes from recycling spent catalytic converters and jewelry.
Handling
Platinum metal is inert and is not considered toxic; it is used in implants and jewelry. Some platinum compounds are hazardous. Soluble platinum salts, such as chloroplatinates, can cause a severe allergy called platinosis, with asthma and skin rashes, in refinery and catalyst workers. Platinum cancer drugs are toxic to the kidneys, nerves and bone marrow and are given only under medical supervision.
Quick answers
Platinum (symbol Pt) is element 78 on the periodic table, a transition metal in period 6, group 10. The catalyst metal: platinum makes reactions happen that would otherwise need impossible conditions. At room temperature it is a solid.
[Xe] 4f¹⁴ 5d⁹ 6s¹, giving 6 occupied shells with the distribution 2, 8, 18, 32, 17, 1.Platinum melts at 2041.4 K (1768.3 °C) and boils at 4098 K (3824.9 °C). That puts it among the most refractory elements — it stays solid at temperatures that vaporise most metals.
The standard atomic weight of platinum is 195.084 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
The most common platinum atom, Pt-195, has 117 neutrons: its mass number, 195, minus its atomic number, 78. It makes up 33.775% of natural platinum. The classroom shortcut, rounded atomic mass (195.084) minus atomic number, gives the same 117.
Platinum has a density of 21.45 g/cm³. Water is 1.0 g/cm³, so a block of platinum is about 21.5× heavier.
Platinum has a Pauling electronegativity of 2.28. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Platinum was discovered in 1735 by Antonio de Ulloa. Origin of the name: Spanish platina, "little silver".
Platinum makes up about 0.005 mg/kg of the Earth's crust — genuinely rare, which is why it is expensive.