Polonium (Po)
metalloidSolid
Peso atomico standard
[209]Configurazione elettronica
[Xe] 6s2 4f14 5d10 6p4Punto di fusione
253,85 °CPunto di ebollizione
961,85 °CDensità
9320 kg/m³Stati di ossidazione
−2, +2, +4, +5, +6Elettronegatività (Pauling)
2Energia di ionizzazione (1ª)
8,41807 eVAnno della scoperta
1898Raggio atomico
190 pmDettagli
Polonium is a very rare, highly radioactive chalcogen below tellurium in group 16. It occurs naturally only in minute amounts as part of uranium and thorium decay chains, chiefly through isotopes such as ²¹⁰Po. Its chemistry combines metallic character with chalcogen behavior, and its significance comes mainly from intense alpha radioactivity rather than from ordinary materials use.
Polonium-210 is a low-melting, fairly volatile metal, 50% of which is vaporized in air in 45 hours at 55°C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 g of radium.
The energy released by its decay is so large (140W/g) that a capsule containing about half a gram reaches a temperature above 500C. The capsule also presents a contact gamma-ray dose rate of 0.012 Gy/h. A few curies (1 curie = 3.7 x 1010Bq) of polonium exhibit a blue glow, caused by excitation of the surrounding gas.
Polonium is readily dissolved in dilute acids, but is only slightly soluble in alkali. Polonium salts of organic acids char rapidly; halide amines are reduced to the metal.
Polonium was discovered by Marie Sklodowska Curie, a Polish chemist, in 1898. She obtained polonium from pitchblende, a material that contains uranium, after noticing that unrefined pitchblende was more radioactive than the uranium that was separated from it. She reasoned that pitchblende must contain at least one other radioactive element. Curie needed to refine several tons of pitchblende in order to obtain tiny amounts of polonium and radium, another radioactive element discovered by Curie. One ton of uranium ore contains only about 100 micrograms (0.0001 grams) of polonium. Due to its scarcity, polonium is usually produced by bombarding bismuth-209 with neutrons in a nuclear reactor. This forms bismuth-210, which has a half-life of 5 days. Bismuth-210 decays into polonium-210 through beta decay. Milligram amounts of polonium-210 have been produced by this method.
Polonium-210 is a very strong emitter of alpha particles. A single gram of polonium-210 creates 140 Watts of heat energy and is being considered as a lightweight heat source for thermoelectric power for spacecraft. Polonium-210 has a half-life of 138.39 days.
Polonium's most stable isotope, polonium-209, has a half-life of 102 years. It decays into lead-205 through alpha decay. Polonium-209 is available from Oak Ridge National Laboratory at the cost of about $3200 per microcurie.
Named after Poland, native country of Madam Curie. Polonium, also called Radium F, was the first element discovered by Curie in 1898 while seeking the cause of radioactivity of pitchblend from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth.
Macroscopic polonium is difficult to handle and observe because it self-heats and rapidly accumulates radiation damage. The pure element is reported as a silvery metal; two solid allotropes are known near ordinary temperatures, including a simple cubic form unusual among elements.
Polonium has no broad commercial use. Historically, ²¹⁰Po was used in static eliminators and neutron sources when mixed with beryllium, where alpha particles drive neutron emission. Such uses have largely been replaced or tightly restricted because of radiological risk and regulatory burden. Small quantities remain relevant for calibration, specialized research, and legacy sealed-source applications.
Polonium can be used to eliminate static electricity in machinery that is caused by processes such as the rolling of paper, wire or sheet metal, although other materials which emit beta particles are more commonly used for this purpose. Polonium is also used in brushes for removing dust from photographic films, although the polonium must be carefully sealed to protect the user from contamination. Polonium is also combined with beryllium to form neutron sources.
Because almost all alpha radiation is stopped within the solid source and its container, giving up its energy, polonium has attracted attention for uses as a lightweight heat source for thermoelectric power in space satellites.
Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. The element has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are both more commonly used and less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user.
Isotopes in Industry
210Po (with a half-life of 138 days) is used as static eliminator to remove static electricity in machinery. This is useful in machinery that produces electricity easily, for example, via rolling paper, manufacturing sheet plastics, and spinning synthetic fibers, which all readily produce static [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf., [563] United States Nuclear Regulatory Commission. Backgrounder on Polonium-210, United States Nuclear Regulatory Commission (2017), April 8; http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/polonium.html.. 210Po can also make use of its static eliminating properties when used in brushes that function to clean camera lenses and photographic films (Fig. IUPAC.84.1) [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf.. 210Po has been used to manufacture atomic weapons. When combined with beryllium, polonium can act as a neutron-producing initiator. However, because of its short half-life, 210Po is no longer used in this manner [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf..
Polonium chemistry is best known for oxidation states −2, +2, +4, and +6, with +4 often prominent in aqueous and halide chemistry. Representative compounds include polonium dioxide, PoO₂, polonium tetrachloride, PoCl₄, and polonium hydride, H₂Po, an unstable hydrogen chalcogenide. Polonides are formed with electropositive metals, but many compounds are hard to study because radiolysis and self-heating alter samples.
See more information at the Polonium compound page.
Polonium is an extreme internal radiological hazard, especially ²¹⁰Po, an alpha emitter. Alpha particles are stopped by skin or thin barriers, but inhaled, ingested, or wound-introduced material can deliver severe localized doses. The element is also chemically toxic, though radiation dominates most risk assessments. Work requires sealed containment, contamination control, and isotope-specific monitoring.
Polonium-210 is very dangerous to handle in even milligram or microgram amounts, and special equipment and strict control is necessary. Damage arises from the complete absorption of the energy of the alpha particle into tissue.
Natural polonium is generated continuously in uranium and thorium decay series and is present at trace levels in rocks, soils, seawater, and the atmosphere. ²¹⁰Po can be transferred through air, water, and food webs, often following particles and sulfur- or selenium-like chemical pathways. It decays rather than persisting indefinitely, but local concentrations can matter in biological and radiological studies.
Polonium is not a traded bulk commodity. Usable ²¹⁰Po is produced in specialized nuclear facilities, commonly by neutron irradiation of bismuth to form ²¹⁰Bi, which decays to ²¹⁰Po, followed by radiochemical separation. Supply is limited by short half-life, licensing, security, and handling costs rather than ore availability. Substitution by less hazardous technologies has sharply reduced routine demand, so production is small and purpose-specific.
Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium.
In 1934, scientists discovered that when they bombarded natural bismuth (209Bi) with neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors.
Polonium has no stable isotopes, so primordial polonium has long since decayed. In space it is expected only as a transient product of radioactive decay chains or nucleosynthesis pathways involving heavy nuclei. Any detectable amount in planetary materials reflects recent generation from longer-lived actinides, not independent cosmic abundance.
- ²¹⁰Po has a half-life of about 138 days, which strongly limits storage and distribution.
- Polonium was identified by Marie and Pierre Curie in pitchblende residues in 1898.
- The name honored Poland, which was not then an independent state.
- Elemental polonium can become warm from its own alpha-decay heat.
- A polonium-beryllium source produces neutrons without requiring a reactor during use.
- Polonium's simple cubic alpha allotrope is rare among elemental crystal structures.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 190 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 140 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 197 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Densità
- 9320 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,0227 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 253,85 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 961,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Struttura cristallina
- Cubica semplice Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 2 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Elettronegatività (Allen)
- 2,19
- Affinità elettronica
- 1,9 eV
- Energia di ionizzazione (1ª)
- 8,41807 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 19,300066 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 27,300094 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 36,000124 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 57,000196 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- −2, +2, +4, +5, +6 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 6 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s2 4f14 5d10 6p4
Termodinamiche
- Calore di fusione
- 0,13473597 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 1,057159 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 1,824118 eV
- Calore di atomizzazione
- 1,824118 eV
Nucleari
- Protoni
- 84 Confronta Protoni di tutti gli elementi →
- Neutroni
- 125 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 42 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 0 Confronta Isotopi stabili di tutti gli elementi →
- Numero di massa (isotopo più stabile)
- 209
- Isotopo più stabile
- Po-209
- Anno della scoperta
- 1898
Abbondanza
- Abbondanza (crosta terrestre)
- 2e-10 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 1,5 × 10−14 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 335 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 32, 18, 6 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-08-6 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 3P2
- InChI
- InChI=1S/Po
- Chiave InChI
- HZEBHPIOVYHPMT-UHFFFAOYSA-N
Configurazione elettronica Misurato
Po: 4f¹⁴ 5d¹⁰ 6s² 6p⁴[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁴Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
Nessun isotopo stabile.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 211 Radioattivo | 210,9866536 ± 0,0000014 | N/D | 516 ms |
| 193 Radioattivo | 192,991026 ± 0,000037 | N/D | 399 ms |
| 194 Radioattivo | 193,988186 ± 0,000014 | N/D | 392 ms |
| 212 Radioattivo | 211,9888684 ± 0,0000013 | N/D | 294.4 ns |
| 188 Radioattivo | 187,999416 ± 0,000021 | N/D | 270 us |
Fase / Stato
Motivo: 228,9 °C sotto il punto di fusione (253,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 84. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| Po I | 0 | 37 | 0 | 4 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| Po I | 0 | 33 |
| Po II | +1 | 2 |
| Po III | +2 | 2 |
| Po IV | +3 | 2 |
| Po V | +4 | 2 |
| Po VI | +5 | 2 |
| Po VII | +6 | 2 |
| Po VIII | +7 | 2 |
| Po IX | +8 | 2 |
| Po X | +9 | 2 |
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +4 | 6 | N/D | 94 pm |
| +4 | 8 | N/D | 108 pm |
| +6 | 6 | N/D | 67 pm |
Composti
Isotopi (5)
Twenty five isotopes of polonium are known, with atomic masses ranging from 194 to 218. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 103 years) and mass 208 (half-life 2.9 years) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 211 Radioattivo | 210,9866536 ± 0,0000014 | N/D | 516 ms | α =100% | |
| 193 Radioattivo | 192,991026 ± 0,000037 | N/D | 399 ms | α ≈100%β+ ? | |
| 194 Radioattivo | 193,988186 ± 0,000014 | N/D | 392 ms | α ≈100%β+ ? | |
| 212 Radioattivo | 211,9888684 ± 0,0000013 | N/D | 294.4 ns | α =100% | |
| 188 Radioattivo | 187,999416 ± 0,000021 | N/D | 270 us | α ≈100%β+ ? |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 145 pm
- Raggio covalente (Pyykkö, legame doppio)
- 135 pm
- Raggio covalente (Pyykkö, legame triplo)
- 129 pm
Raggi di van der Waals
- Truhlar
- 197 pm
- UFF
- 470,9 pm
- MM3
- 259 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 250 pm
Scale di numerazione
- Mendeleev
- 103
- Pettifor
- 91
- Glawe
- 93
Scale di elettronegatività
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 6
- Robles–Bartolotti
- 4
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 44 a.u.
- Polarizzabilità dipolare (inc.)
- 4 a.u.
- C₆ (Gould–Bučko)
- 424 Ha·Bohr6
Transizioni di fase e allotropi
| Punto di fusione | 527,15 K |
| Punto di ebollizione | 1235,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (15)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 1,6232 |
| 2 | p | 4,5428 |
| 2 | s | 22,0782 |
| 3 | d | 13,428 |
| 3 | p | 23,2851 |
| 3 | s | 24,3813 |
| 4 | d | 36,3328 |
| 4 | f | 37,8416 |
| 4 | p | 36,3328 |
| 4 | s | 35,4784 |
Dettaglio dei raggi cristallini (3)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 4 | VI | 108 | from r^3 vs V plots, | |
| 4 | VIII | 122 | from r^3 vs V plots, | |
| 6 | VI | 81 | Ahrens (1952) ionic radius, |
Modalità di decadimento degli isotopi (71)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 186 | A | 100% |
| 186 | p | — |
| 187 | A | 100% |
| 187 | B+ | — |
| 188 | A | 100% |
| 188 | B+ | — |
| 189 | A | 100% |
| 189 | B+ | — |
| 190 | A | 100% |
| 190 | B+ | — |
Fattori di diffusione dei raggi X (516)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 4,92763 |
| 10,1617 | — | 4,95784 |
| 10,3261 | — | 4,98823 |
| 10,4931 | — | 5,01881 |
| 10,6628 | — | 5,04957 |
| 10,8353 | — | 5,10634 |
| 11,0106 | — | 5,17368 |
| 11,1886 | — | 5,24191 |
| 11,3696 | — | 5,31104 |
| 11,5535 | — | 5,38108 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
2×10-10 milligrams per kilogram
Riferimenti (1)
- [5] Polonium https://education.jlab.org/itselemental/ele084.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.5×10-14 milligrams per liter
Riferimenti (1)
- [5] Polonium https://education.jlab.org/itselemental/ele084.html
Sources
Sources of this element.
Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium.
In 1934, scientists discovered that when they bombarded natural bismuth (209Bi) with neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors.
Riferimenti (1)
- [6] Polonium https://periodic.lanl.gov/84.shtml
Riferimenti
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Polonium.
The element property data was retrieved from publications.