Polonium
Polonium is a rare, intensely radioactive metalloid that was the first new element Marie and Pierre Curie discovered while searching for the source of unexplained radioactivity in uranium ore. It exists in nature only in minute traces, as a fleeting step in the radioactive decay chains of uranium and thorium, and virtually all of it studied today has to be produced artificially.
- Group · Period
- 16 · 6
- At room temp
- solid
- Melts at
- 527 K
- Density
- 9.32 g/cm³
- Discovered
- 1898
Uses
Because it’s so intensely radioactive and hazardous, polonium has almost no large-scale industrial use, and what limited applications exist are tightly controlled. Small amounts of polonium-210 have been used in industrial anti-static devices, called static eliminators, that use its radiation to neutralize static charge on things like photographic film and paper during manufacturing. Its enormous heat output relative to its size also once made it useful as a compact power source for specialized scientific equipment, including some heaters used in early Soviet space missions, though longer-lived heat sources have generally replaced it for that purpose.
Polonium is otherwise studied mainly for scientific and safety research — understanding its behavior matters for radiation protection, nuclear science, and, notoriously, forensic toxicology, given its history of use as a poison.
History
Polonium was discovered in 1898 by Marie and Pierre Curie while they were investigating why uranium ore was more radioactive than the uranium it contained could account for. Working through the ore’s components, they isolated a new, intensely radioactive substance and named it polonium after Poland, Marie Curie’s home country, which at the time did not exist as an independent nation. It was the first of two new elements the Curies discovered that year, the second being radium, and the discovery helped establish radioactivity as a property of specific atoms rather than a bulk material effect.
Fun facts
- Polonium was the first element Marie and Pierre Curie discovered, in 1898, and Marie named it after her native Poland to draw international attention to its lack of political independence at the time.
- Polonium is so radioactive that a gram of it can heat itself to hundreds of degrees Celsius purely from its own radioactive decay, with no external heat source.
- Polonium-210 became internationally notorious in 2006 after it was used to poison former Russian intelligence officer Alexander Litvinenko.
Frequently asked questions
Why is polonium so dangerous if you can't see or smell it?
Polonium mainly emits alpha radiation, which can't penetrate skin and is barely dangerous from outside the body. The real danger comes if it's inhaled, swallowed, or otherwise gets inside the body, where even a tiny amount can cause severe internal radiation damage — which is exactly what made it so hazardous in the 2006 Litvinenko poisoning case.
Does polonium have any legitimate uses?
Yes, in small, tightly controlled amounts. Polonium-210's intense heat output has been used to power compact radioisotope heaters, such as those that kept some Soviet lunar rover equipment warm, and small amounts are used in industrial devices that eliminate static electricity by ionizing air.
How did Marie Curie find an element that occurs in such tiny amounts?
Curie and her husband Pierre painstakingly processed tons of uranium ore, tracking the radioactivity at every step, because polonium exists in that ore only in vanishingly small traces. Their patient, repetitive chemistry eventually concentrated enough of it to confirm it was a genuinely new, highly radioactive element.
Compounds
2 notable compounds containing Po
- PoO2oxide
Polonium dioxide
A yellow (low-temperature) or black (high-temperature) solid formed by heating polonium metal in oxygen, and one of the small handful of polonium compounds characterized in any detail, owing to how little polonium exists to study at once.
Used for: Studied mainly for fundamental research into polonium's chemistry
- PoCl4salt
Polonium tetrachloride
A bright yellow, water-soluble solid and the best-characterized of polonium's halides, prepared and studied only ever in microgram quantities because of polonium's intense radioactivity.
Used for: Used in tracer-scale studies of polonium's chemical behavior
Isotopes
42 known isotopes
Swipe to see all columns →
| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| Po-208 | — | 2.898 Y | Alpha decay (99.996%), Electron capture / beta-plus decay (0.004%) | -17,469.21 keV | 7,839.36 keV | 4.99 × 10-24 eV |
| Po-209 | — | 124 Y | Alpha decay (99.546%), Electron capture / beta-plus decay (0.454%) | -16,366.02 keV | 7,835.19 keV | 1.17 × 10-25 eV |
| Po-210 | — | 138.376 d | Alpha decay (100%) | -15,953.06 keV | 7,834.35 keV | 3.82 × 10-23 eV |
Show all 42 isotopes
| Po-186 | — | 28 us | Alpha decay (100%) | 4,101.53 keV | 7,695.95 keV | 1.63 × 10-11 eV |
| Po-187 | — | 1.40 ms | Alpha decay (100%) | 2,823.81 keV | 7,704.79 keV | 3.26 × 10-13 eV |
| Po-188 | — | 0.27 ms | Alpha decay (100%) | -544.38 keV | 7,724.65 keV | 1.69 × 10-12 eV |
| Po-189 | — | 3.5 ms | Alpha decay (100%) | -1,422 keV | 7,731.13 keV | 1.30 × 10-13 eV |
| Po-190 | — | 2.45 ms | Alpha decay (100%) | -4,562.71 keV | 7,749.45 keV | 1.86 × 10-13 eV |
| Po-191 | — | 22 ms | Alpha decay (99%) | -5,068.73 keV | 7,753.79 keV | 2.07 × 10-14 eV |
| Po-192 | — | 32.2 ms | Alpha decay (99.5%), Electron capture / beta-plus decay (0.5%) | -8,066.48 keV | 7,771.05 keV | 1.42 × 10-14 eV |
| Po-193 | — | 399 ms | Alpha decay (100%) | -8,325.3 keV | 7,773.95 keV | 1.14 × 10-15 eV |
| Po-194 | — | 0.392 s | Alpha decay (93%), Electron capture / beta-plus decay (7%) | -11,004.62 keV | 7,789.29 keV | 1.16 × 10-15 eV |
| Po-195 | — | 4.64 s | Alpha decay (94%), Electron capture / beta-plus decay (6%) | -11,116.66 keV | 7,791.32 keV | 9.83 × 10-17 eV |
| Po-196 | — | 5.8 s | Alpha decay (98%), Electron capture / beta-plus decay (2%) | -13,468.73 keV | 7,804.74 keV | 7.87 × 10-17 eV |
| Po-197 | — | 84 s | Electron capture / beta-plus decay (56%), Alpha decay (44%) | -13,393.08 keV | 7,805.71 keV | 5.43 × 10-18 eV |
| Po-198 | — | 1.760 m | Alpha decay (57%), Electron capture / beta-plus decay (43%) | -15,473.28 keV | 7,817.56 keV | 4.32 × 10-18 eV |
| Po-199 | — | 5.47 m | Electron capture / beta-plus decay (92.5%), Alpha decay (7.5%) | -15,238.83 keV | 7,817.66 keV | 1.39 × 10-18 eV |
| Po-200 | — | 11.51 m | Electron capture / beta-plus decay (88.9%), Alpha decay (11.1%) | -16,941.68 keV | 7,827.44 keV | 6.61 × 10-19 eV |
| Po-201 | — | 15.50 m | Electron capture / beta-plus decay (98.87%), Alpha decay (1.13%) | -16,521.17 keV | 7,826.56 keV | 4.91 × 10-19 eV |
| Po-202 | — | 44.6 m | Electron capture / beta-plus decay (98.08%), Alpha decay (1.92%) | -17,941.57 keV | 7,834.81 keV | 1.70 × 10-19 eV |
| Po-203 | — | 36.7 m | Electron capture / beta-plus decay (99.89%), Alpha decay (0.11%) | -17,310.82 keV | 7,832.86 keV | 2.07 × 10-19 eV |
| Po-204 | — | 3.519 h | Electron capture / beta-plus decay (99.33%), Alpha decay (0.67%) | -18,341.05 keV | 7,839.08 keV | 3.60 × 10-20 eV |
| Po-205 | — | 1.74 h | Electron capture / beta-plus decay (99.96%), Alpha decay (0.04%) | -17,521.4 keV | 7,836.22 keV | 7.28 × 10-20 eV |
| Po-206 | — | 8.8 d | Electron capture / beta-plus decay (94.55%), Alpha decay (5.45%) | -18,188.67 keV | 7,840.6 keV | 6.00 × 10-22 eV |
| Po-207 | — | 5.80 h | Electron capture / beta-plus decay (99.979%), Alpha decay (0.021%) | -17,145.7 keV | 7,836.67 keV | 2.19 × 10-20 eV |
| Po-211 | — | 0.516 s | Alpha decay (100%) | -12,432.49 keV | 7,818.78 keV | 8.84 × 10-16 eV |
| Po-212 | — | 294.3 ns | Alpha decay (100%) | -10,369.41 keV | 7,810.24 keV | 1.55 × 10-9 eV |
| Po-213 | — | 3.706 us | Alpha decay (100%) | -6,653.52 keV | 7,794.02 keV | 1.23 × 10-10 eV |
| Po-214 | — | 163.46 us | Alpha decay (100%) | -4,469.97 keV | 7,785.12 keV | 2.79 × 10-12 eV |
| Po-215 | — | 1.781 ms | Alpha decay (99.99977%), Beta-minus decay (0.00023%) | -541.77 keV | 7,768.18 keV | 2.56 × 10-13 eV |
| Po-216 | — | 0.145 s | Alpha decay (100%) | 1,782.34 keV | 7,758.82 keV | 3.15 × 10-15 eV |
| Po-217 | — | 1.53 s | Alpha decay (95%), Beta-minus decay (5%) | 5,883.45 keV | 7,741.36 keV | 2.98 × 10-16 eV |
| Po-218 | — | 3.097 m | Alpha decay (99.98%), Beta-minus decay (0.02%) | 8,356.65 keV | 7,731.53 keV | 2.46 × 10-18 eV |
| Po-219 | — | 620 s | Beta-minus decay (71.8%), Alpha decay (28.2%) | 12,681.36 keV | 7,713.33 keV | 7.36 × 10-19 eV |
| Po-220 | — | 300 ns | Beta-minus decay | 15,263.46 keV | 7,703.22 keV | 1.52 × 10-9 eV |
| Po-221 | — | 112 s | Beta-minus decay (100%) | 19,773.76 keV | 7,684.48 keV | 4.07 × 10-18 eV |
| Po-222 | — | 550 s | Unknown | 22,486.27 keV | 7,674.01 keV | 8.30 × 10-19 eV |
| Po-223 | — | 300 ns | Beta-minus decay | 27,079 keV | 7,655 keV | 1.52 × 10-9 eV |
| Po-224 | — | — | Beta-minus decay (100%) | 29,910 keV | 7,644 keV | — |
| Po-225 | — | 300 ns | Beta-minus decay | 34,580 keV | 7,626 keV | 1.52 × 10-9 eV |
| Po-226 | — | 300 ns | Beta-minus decay | 37,549 keV | 7,614 keV | 1.52 × 10-9 eV |
| Po-227 | — | 300 ns | Beta-minus decay | 42,281 keV | 7,596 keV | 1.52 × 10-9 eV |