Polonium dichloride
Encyclopedia
Polonium dichloride is a chemical compound
of the radioactive metal polonium
and chlorine
. Its chemical formula
is PoCl2.
, although this is likely a pseudo-cell. Alternatively, the true space group may be monoclinic or triclinic, with one or more cell angles close to 90°. Assuming the space group is P222, the structure exhibits distorted cubic coordination of Po as {PoCl8} and distorted square planar coordination of Cl as {ClPo4}.
of polonium metal or by dehalogenation of polonium tetrachloride, PoCl4. Methods for dehalogenating PoCl4 include thermal decomposition at 300 °C, reduction of cold, slightly moist PoCl4 by sulfur dioxide
; and heating PoCl4 in a stream of carbon monoxide
or hydrogen sulfide
at 150 °C.
to give a pink solution, which autoxidises
to Po(IV). PoCl2 is rapidly oxidised by hydrogen peroxide
or chlorine water. Addition of potassium hydroxide
to the pink solution results in a dark brown precipitate – possibly hydrated PoO or Po(OH)2 – which is rapidly oxidised to Po(IV). With dilute nitric acid
, PoCl2 forms a dark red solution followed by a flaky white precipitate of unknown composition.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
of the radioactive metal polonium
Polonium
Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Skłodowska-Curie and Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for...
and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
. Its chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
is PoCl2.
Structure
Polonium dichloride appears to crystallise with an orthorhombic unit cell in either the P222, Pmm2 or Pmmm space groupSpace group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
, although this is likely a pseudo-cell. Alternatively, the true space group may be monoclinic or triclinic, with one or more cell angles close to 90°. Assuming the space group is P222, the structure exhibits distorted cubic coordination of Po as {PoCl8} and distorted square planar coordination of Cl as {ClPo4}.
Preparation
PoCl2 can be obtained either by halogenationHalogenation
Halogenation is a chemical reaction that incorporates a halogen atom into a molecule in substitution of hydrogen atom. Halogenation takes place in the gas phase. There are four types of halogenation: fluorination, chlorination, bromination, and iodination...
of polonium metal or by dehalogenation of polonium tetrachloride, PoCl4. Methods for dehalogenating PoCl4 include thermal decomposition at 300 °C, reduction of cold, slightly moist PoCl4 by sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
; and heating PoCl4 in a stream of carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
or hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
at 150 °C.
Reactions
PoCl2 dissolves in dilute hydrochloric acidHydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
to give a pink solution, which autoxidises
Autoxidation
Autoxidation is any oxidation that occurs in open air or in presence of oxygen and/or UV radiation and forms peroxides and hydroperoxides. A classic example of autoxidation is that of simple ethers like diethyl ether, whose peroxides can be dangerously explosive. It can be considered to be a slow,...
to Po(IV). PoCl2 is rapidly oxidised by hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
or chlorine water. Addition of potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
to the pink solution results in a dark brown precipitate – possibly hydrated PoO or Po(OH)2 – which is rapidly oxidised to Po(IV). With dilute nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, PoCl2 forms a dark red solution followed by a flaky white precipitate of unknown composition.