Polonium

Polonium - Po

CAS: 7440-08-6
Description:Radioactive metalloid
Classification: Metalloid
Date of Discovery: 1898
Discoverer: Pierre and Marie Curie
Name Origin: Poland, native country of Mme. Curie

Atomic Number: 84
Number of Neutrons: 125
Atomic Mass: (209) amu
Melting Point: 254 °C
Boiling Point: 962 °C
Density (293 K): 9.32 g/cm³ (

)
Atomic volume: 22.23 cm³/mol
Electrical resistivity: 0.0219 10^-6/cm

Thermal conductivity: 0.20 W/cmK
Enthalpy of atomization: 134 kJ/mol
Enthalpy of vaporization: 60.3 kJ/mol
Enthalpy of fusion:
Specific heat capacity: 0.12 J/gK

Energy levels: 2-8-18-32-18-6
Electron configuration: [Xe]4f ¹⁴5d¹⁰6s²6p⁴
Crystal Structure: Monoclinic
Atomic radius: 1.53 Å
Covalent radius: 1.46 Å
Oxidation States: -2, 0, +2, +3(?), +4, and +6
Electronegativity, Pauling: 2.0
Electron affinity: 1.9 eV
First ionization energy: 8.42 eV
2nd ionization energy:
3rd ionization energy:
Polarizability: 6.8 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
¹⁹²Po	191.9915	34 ms
^193mPo	0.24 s
¹⁹³Po	192.9911	0.45 s
¹⁹⁴Po	193.9883	0.39 s		0+
^195mPo	1.9 s
¹⁹⁵Po	194.9881	4.6 s
¹⁹⁶Po	195.9855	5.8 s	; ⁺, EC	0+
^197mPo	25.8 s	; ⁺, EC	13/2+
¹⁹⁷Po	196.9856	53 s	; ⁺, EC	3/2-
¹⁹⁸Po	197.9834	1.76 m	; ⁺, EC	0+
^199mPo	4.2 m	⁺, EC;	13/2+
¹⁹⁹Po	198.985	5.2 m	⁺, EC;	(3/2-)
²⁰⁰Po	199.9817	11.5 m	⁺, EC;	0+
^201mPo	8.9 m	⁺, EC; IT;
²⁰¹Po	200.9822	15.3 m	⁺, EC;	3/2-
²⁰²Po	201.9807	45 m	⁺, EC;	0+
^203mPo	1.2 m	IT; ^-, EC	13/2+
²⁰³Po	202.9814	35 m	⁺, EC	5/2-
²⁰⁴Po	203.98031	3.53 h	EC;	0+
²⁰⁵Po	204.98117	1.7 h	⁺, EC	5/2-
²⁰⁶Po	205.98047	8.8 d	EC;	0+
^207mPo	2.8 s	IT	19/2-
²⁰⁷Po	206.98158	5.80 h	EC, ⁺	5/2-
²⁰⁸Po	207.981231	2.898 y		0+
²⁰⁹Po	208.982415	102 y		1/2-
²¹⁰Po	209.982857	138.38 d		0+
^211mPo	25.2 s		25/2+
²¹¹Po	210.986637	0.516 s		9/2+
^212mPo	45 s		16+
²¹²Po	211.988852	0.298 µs		0+
²¹³Po	212.992843	4 µs		9/2+
²¹⁴Po	213.995186	163.7 µs		0+
²¹⁵Po	214.999415	1.780 ms		(9/2+)
²¹⁶Po	216.001905	0.145 s		0+
²¹⁷Po	217.0064	< 10 s
²¹⁸Po	218.008965	3.04 m		0+
Polonium was the first element discovered by Mme. Curie in 1898, while seeking the cause of radioactivity of pitchblende from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth. Polonium is also called Radium F. Polonium is a very rare natural element. Uranium ores contain only about 100 µg of the element per ton. Its abundance is only about 0.2% of that of radium. In 1934, it was found that when natural bismuth (²⁰⁹Bi) was bombarded by 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-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 (140 W/g) that a capsule containing about half a gram reaches a temperature above 500 ° C. 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. 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. Thirty-six isotopes and isomers of polonium are known, with atomic masses ranging from 192 to 218. All are radioactive. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 102 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. Metallic polonium has been prepared from polonium hydroxide and some other polonium compounds in the presence of concentrated aqueous or anhydrous liquid ammonia. Two allotropic modifications are known to exist. Polonium is readily dissolved in dilute acids, but is only slightly soluble in alkalis. Polonium salts of organic acids char rapidly; halide amines are reduced to the metal. Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. It has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are more commonly used and are 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. 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. The maximum permissible body burden for ingested polonium is only 0.03 µCi, which represents a particle weighing only 6.8 x 10^-12 g. Weight for weight it is about 2.5 x 10¹¹ times as toxic as hydrocyanic acid. The maximum allowable concentration for soluble polonium compounds in air is about 2 x 10¹¹ µCi/cm³. LINKS: A Biography of Marie Curie Marine Bioradiochemistry Laboratory Nuclear Twins: The Discovery of the Proton and Neutron The Polonium-218 Controversy Polonium Halos: Evidence For Earth's Instant Creation? Science in Poland - Maria Sklodowska-Curie Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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