Europium(II) iodide is the
iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
salt of divalent
europium
Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
cation.
Preparation
Europium(II) iodide can be prepared in a handful of ways, including:
Reduction of
europium(III) iodide
Europium(III) iodide is an inorganic compound containing europium and iodine with the chemical formula .
Preparation
Europium metal reacts directly with iodine to form europium(III) iodide:
:
Hydrated europium(III) iodide can be prepared dissolv ...
with
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
gas at 350 °C:
:
Thermal decomposition of
europium(III) iodide
Europium(III) iodide is an inorganic compound containing europium and iodine with the chemical formula .
Preparation
Europium metal reacts directly with iodine to form europium(III) iodide:
:
Hydrated europium(III) iodide can be prepared dissolv ...
at 200 °C:
:
Reaction of europium with
mercury(II) iodide
Mercury(II) iodide is a chemical compound with the molecular formula Hg I2. It is typically produced synthetically but can also be found in nature as the extremely rare mineral coccinite. Unlike the related mercury(II) chloride it is hardly solu ...
:
:
Reaction of europium with
ammonium iodide
Ammonium iodide is the chemical compound NH4I. It is used in photographic chemicals and some medications.Holleman, A. F.; Wiberg, E. ''Inorganic Chemistry'' Academic Press: San Diego, 2001. . It can be prepared by the action of hydroiodic acid on a ...
:
:
Structure
Europium(II) iodide has several
polymorphs.
It adopts a
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
in
space group P 21/c (no. 14).
It also adopts an
orthorhombic polymorph in
space group ''Pbca'' (no. 61). This form is
isostructural Isostructural chemical compounds have similar chemical structures. "Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous s ...
with
strontium iodide
Strontium iodide (SrI2) is a salt of strontium and iodine. It is an ionic, water-soluble, and deliquescent compound that can be used in medicine as a substitute for potassium iodide
.
It is also used as a scintillation gamma radiation detector, ...
.
A third polymorph of europium(II) iodide is formed if it is prepared from europium and ammonium iodide at low temperatures (200 K) in
liquid ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wast ...
. This low-temperature phase is
orthorhombic and in
space group ''Pnma'' (no. 62). This is the same structure as modification IV of strontium iodide.
References
Europium(II) compounds
Iodides
Lanthanide halides
{{Inorganic-compound-stub